deploy: f0d5e17be72cb5853da24c530d98a5e7bc0072e8

files/blog/leetcode/sort-matrix-diagonally/makefile

@@ -0,0 +1,16 @@
+CXX=clang++
+CXXFLAGS=-std=c++20 -Wall -Wextra -Werror -g -pedantic
+
+test: matrix-sort
+	./matrix-sort
+
+matrix-sort: format tidy
+	$(CXX) $(CXXFLAGS) matrix-sort.cpp -o matrix-sort
+
+format:
+	clang-format -i -style=webkit *.cpp
+
+tidy:
+	clang-tidy *.cpp -- $(CXXFLAGS)
+
+.PHONY: matrix-sort format tidy

files/blog/leetcode/sort-matrix-diagonally/matrix-sort.cpp

@@ -0,0 +1,229 @@
+#include <algorithm>
+#include <cassert>
+#include <vector>
+
+using matrix = std::vector<std::vector<int>>;
+
+template <typename T>
+class diagonal {
+    using matrix_t = std::vector<std::vector<T>>;
+
+    matrix_t& matrix;
+    std::size_t x;
+    std::size_t y;
+
+    class diagonal_iter {
+        // we need to keep reference to the matrix itself
+        std::reference_wrapper<matrix_t> m;
+
+        // we need to be able to tell our current position
+        std::size_t x;
+        std::size_t y;
+
+    public:
+        using difference_type = std::ptrdiff_t;
+        using value_type = T;
+        using pointer = T*;
+        using reference = T&;
+        using iterator_category = std::random_access_iterator_tag;
+
+        diagonal_iter(matrix_t& matrix,
+            std::size_t x,
+            std::size_t y)
+            : m(matrix)
+            , x(x)
+            , y(y)
+        {
+        }
+
+        bool operator==(const diagonal_iter& rhs) const
+        {
+            return x == rhs.x && y == rhs.y && m.get() == rhs.m.get();
+        }
+
+        diagonal_iter& operator++()
+        {
+            // we are moving along the diagonal, so we increment both ‹x› and ‹y›
+            // at the same time
+            x++;
+            y++;
+            return *this;
+        }
+
+        reference operator*() const { return m.get()[y][x]; }
+
+        // exactly opposite to the incrementation
+        diagonal_iter operator--()
+        {
+            x--;
+            y--;
+            return *this;
+        }
+
+        // moving ‹n› steps back is same as calling decrementation ‹n›-times, so
+        // we can just return a new iterator and subtract ‹n› from both
+        // coordinates in the matrix
+        diagonal_iter operator-(difference_type n) const
+        {
+            return diagonal_iter { m, x - n, y - n };
+        }
+
+        // here we assume that we are given two iterators on the same diagonal
+        difference_type operator-(const diagonal_iter& rhs) const
+        {
+            assert(m.get() == rhs.m.get());
+            return x - rhs.x;
+        }
+
+        // counterpart of moving ‹n› steps backwards
+        diagonal_iter operator+(difference_type n) const
+        {
+            return diagonal_iter { m, x + n, y + n };
+        }
+
+        // we compare the coordinates, and also assume that those 2 iterators are
+        // lying on the same diagonal
+        bool operator<(const diagonal_iter& rhs) const
+        {
+            assert(m.get() == rhs.m.get());
+            return x < rhs.x && y < rhs.y;
+        }
+    };
+
+public:
+    diagonal(matrix_t& matrix, std::size_t x, std::size_t y)
+        : matrix(matrix)
+        , x(x)
+        , y(y)
+    {
+    }
+
+    diagonal_iter begin() const { return diagonal_iter { matrix, x, y }; }
+
+    diagonal_iter end() const
+    {
+        auto max_x = matrix[y].size();
+        auto max_y = matrix.size();
+
+        // we need to find the distance in which we get out of bounds (either in
+        // column or row)
+        auto steps = std::min(max_x - x, max_y - y);
+
+        return diagonal_iter { matrix, x + steps, y + steps };
+    }
+};
+
+template <typename T>
+class diagonals {
+    using matrix_t = std::vector<std::vector<T>>;
+
+    class diagonals_iter {
+        matrix_t& m;
+        std::size_t x;
+        std::size_t y;
+
+    public:
+        diagonals_iter(matrix_t& matrix, std::size_t x, std::size_t y)
+            : m(matrix)
+            , x(x)
+            , y(y)
+        {
+        }
+
+        bool operator!=(const diagonals_iter& rhs) const
+        {
+            // iterators are not equal if they reference different matrices, or
+            // their positions differ
+            return x != rhs.x || y != rhs.y || m != rhs.m;
+        }
+
+        diagonals_iter& operator++()
+        {
+            if (y != 0) {
+                // iterating through diagonals down the first column
+                y++;
+                return *this;
+            }
+
+            // iterating the diagonals along the first row
+            x++;
+            if (x == m.front().size()) {
+                // switching to diagonals in the first column
+                x = 0;
+                y++;
+            }
+
+            return *this;
+        }
+
+        diagonal<T> operator*() const { return diagonal { m, x, y }; }
+    };
+
+    matrix_t& _matrix;
+
+public:
+    diagonals(matrix_t& m)
+        : _matrix(m)
+    {
+    }
+    diagonals_iter begin() { return diagonals_iter { _matrix, 0, 0 }; }
+    diagonals_iter end() { return diagonals_iter { _matrix, 0, _matrix.size() }; }
+};
+
+class Solution {
+public:
+    matrix diagonalSort(matrix mat)
+    {
+        // we iterate over the diagonals
+        for (auto d : diagonals(mat)) {
+            // and we sort each diagonal
+            std::sort(d.begin(), d.end());
+        }
+
+        // we take the matrix by copy, so we can sort in-situ and return the copy
+        // that we sorted
+        return mat;
+    }
+};
+
+static void test_case_1()
+{
+    // Input: mat = [[3,3,1,1],[2,2,1,2],[1,1,1,2]]
+    // Output: [[1,1,1,1],[1,2,2,2],[1,2,3,3]]
+
+    Solution s;
+    assert((s.diagonalSort(std::vector { std::vector { 3, 3, 1, 1 },
+                std::vector { 2, 2, 1, 2 },
+                std::vector { 1, 1, 1, 2 } })
+        == std::vector { std::vector { 1, 1, 1, 1 },
+            std::vector { 1, 2, 2, 2 },
+            std::vector { 1, 2, 3, 3 } }));
+}
+
+static void test_case_2()
+{
+    // Input: mat =
+    // [[11,25,66,1,69,7],[23,55,17,45,15,52],[75,31,36,44,58,8],[22,27,33,25,68,4],[84,28,14,11,5,50]]
+    // Output:
+    // [[5,17,4,1,52,7],[11,11,25,45,8,69],[14,23,25,44,58,15],[22,27,31,36,50,66],[84,28,75,33,55,68]]
+
+    Solution s;
+    assert((s.diagonalSort(std::vector { std::vector { 11, 25, 66, 1, 69, 7 },
+                std::vector { 23, 55, 17, 45, 15, 52 },
+                std::vector { 75, 31, 36, 44, 58, 8 },
+                std::vector { 22, 27, 33, 25, 68, 4 },
+                std::vector { 84, 28, 14, 11, 5, 50 } })
+        == std::vector { std::vector { 5, 17, 4, 1, 52, 7 },
+            std::vector { 11, 11, 25, 45, 8, 69 },
+            std::vector { 14, 23, 25, 44, 58, 15 },
+            std::vector { 22, 27, 31, 36, 50, 66 },
+            std::vector { 84, 28, 75, 33, 55, 68 } }));
+}
+
+int main()
+{
+    test_case_1();
+    test_case_2();
+
+    return 0;
+}

files/ib002/algorithms-correctness/postcondition-ambiguity/test_sort.py

@@ -0,0 +1,139 @@
+from hypothesis import given, settings
+from hypothesis.strategies import integers, lists
+import pytest
+
+import itertools
+
+
+def compare_by_value(pair):
+    """
+    Takes a pair from enumerate in form: `index, value` and returns the value
+
+    Args:
+        pair (Tuple[int, T]): Index and element from the iterator at the index.
+
+    Returns:
+        Element from the pair.
+    """
+    index, value = pair
+    return value
+
+
+def maximum(arr, n):
+    """
+    Finds index of maximum element of first n elements in list.
+
+    Args:
+        arr (List): List of values.
+        n (int): Upper bound of index where to search for maximum (inclusive).
+
+    Returns:
+        Index of a maximum element in `arr[:n]`.
+    """
+    first_n_elements = itertools.islice(enumerate(arr), n)
+    index, value = max(first_n_elements, key=compare_by_value)
+    return index
+
+
+# Precondition: n = |A|
+# Loop invariant:
+#     A[i + 1 : n] is sorted AND
+#     all elements of A[i + 1 : n] are bigger or equal to the other elements
+# Postcondition: A is sorted
+def select_sort(arr, n):
+    """
+    Sorts list `arr` using select sort algorithm.
+
+    Args:
+        arr (List): List of values.
+        n (int): Size of the list.
+
+    Returns:
+        Sorted list `arr`.
+    """
+    assert n == len(arr)
+
+    check_loop_invariant(arr, n, n)
+    for i in reversed(range(1, n)):
+        j = maximum(arr, i + 1)
+        arr[i], arr[j] = arr[j], arr[i]
+
+        check_loop_invariant(arr, n, i)
+
+    return arr
+
+
+def broken_select_sort(arr, n):
+    assert n == len(arr)
+
+    if not arr:
+        return
+
+    max_value = max(arr)
+
+    check_loop_invariant(arr, n, n)
+    for i in reversed(range(n)):
+        arr[i] = max_value + i
+
+        check_loop_invariant(arr, n, i)
+
+    return arr
+
+
+def check_loop_invariant(arr, n, i):
+    # A[i + 1 : n] is sorted
+    for x, y in zip(itertools.islice(arr, i + 1, n), itertools.islice(arr, i + 2, n)):
+        assert x <= y
+
+    # all elements of A[i + 1 : n] are bigger or equal to the other elements
+    if i + 1 >= n:
+        # in case there are no elements
+        return
+
+    # otherwise, since the "tail" is sorted, we can assume that it is enough to
+    # check the other elements to the smallest value of the tail
+    smallest = arr[i + 1]
+    for element in itertools.islice(arr, i + 1):
+        assert smallest >= element
+
+
+def check_vague_postcondition(original_arr, arr):
+    if not arr:
+        return
+
+    # check ordering
+    for x, y in zip(arr, itertools.islice(arr, 1, len(arr))):
+        assert x <= y
+
+
+def check_postcondition(original_arr, arr):
+    if not arr:
+        return
+
+    # check ordering
+    for x, y in zip(arr, itertools.islice(arr, 1, len(arr))):
+        assert x <= y
+
+    # get counts from original list
+    original_counts = {}
+    for value in original_arr:
+        original_counts[value] = 1 + original_counts.get(value, 0)
+
+    # get counts from resulting list
+    counts = {}
+    for value in arr:
+        counts[value] = 1 + counts.get(value, 0)
+
+    # if arr is permutation of original_arr then all counts must be the same
+    assert counts == original_counts
+
+
+@given(lists(integers()))
+@settings(max_examples=1000)
+@pytest.mark.parametrize(
+    "postcondition", [check_vague_postcondition, check_postcondition]
+)
+@pytest.mark.parametrize("sorting_function", [select_sort, broken_select_sort])
+def test_select_sort(sorting_function, postcondition, numbers):
+    result = sorting_function(numbers[:], len(numbers))
+    postcondition(numbers, result)

files/ib002/graphs/bfs-tree/bfs_graph.dot

@@ -0,0 +1,17 @@
+graph {
+    a -- c
+    a -- e
+
+    c -- i
+    c -- b
+
+    e -- j
+
+    i -- d
+
+    b -- h
+
+    d -- h
+
+    h -- j
+}

files/ib002/graphs/bfs-tree/bfs_graph_with_additional_edge.dot

@@ -0,0 +1,18 @@
+graph {
+    a -- c
+    a -- e
+
+    c -- i
+    c -- b
+
+    e -- j
+    e -- h
+
+    i -- d
+
+    b -- h
+
+    d -- h
+
+    h -- j
+}

files/ib002/graphs/bfs-tree/bfs_tree.dot

@@ -0,0 +1,13 @@
+digraph {
+    a -> c
+    a -> e
+
+    c -> b
+    c -> i
+
+    e -> j
+
+    b -> h
+
+    i -> d
+}

files/ib002/graphs/bfs-tree/bfs_tree_with_additional_edge.dot

@@ -0,0 +1,12 @@
+digraph {
+    a -> c
+    a -> e
+
+    c -> b
+    c -> i
+
+    e -> h
+    e -> j
+
+    i -> d
+}

files/ib002/graphs/iterative-and-iterators/.editorconfig

@@ -0,0 +1,206 @@
+# Remove the line below if you want to inherit .editorconfig settings from higher directories
+root = true
+
+# C# files
+[*.cs]
+
+#### Core EditorConfig Options ####
+
+# Indentation and spacing
+indent_size = 4
+indent_style = space
+tab_width = 4
+
+# New line preferences
+end_of_line = lf
+insert_final_newline = true
+
+#### .NET Coding Conventions ####
+
+# Organize usings
+dotnet_separate_import_directive_groups = false
+dotnet_sort_system_directives_first = false
+file_header_template = unset
+
+# this. and Me. preferences
+dotnet_style_qualification_for_event = false:silent
+dotnet_style_qualification_for_field = false:silent
+dotnet_style_qualification_for_method = false:silent
+dotnet_style_qualification_for_property = false:silent
+
+# Language keywords vs BCL types preferences
+dotnet_style_predefined_type_for_locals_parameters_members = true:silent
+dotnet_style_predefined_type_for_member_access = true:silent
+
+# Parentheses preferences
+dotnet_style_parentheses_in_arithmetic_binary_operators = always_for_clarity:silent
+dotnet_style_parentheses_in_other_binary_operators = always_for_clarity:silent
+dotnet_style_parentheses_in_other_operators = never_if_unnecessary:silent
+dotnet_style_parentheses_in_relational_binary_operators = always_for_clarity:silent
+
+# Modifier preferences
+dotnet_style_require_accessibility_modifiers = for_non_interface_members:silent
+
+# Expression-level preferences
+dotnet_style_coalesce_expression = true:suggestion
+dotnet_style_collection_initializer = true:suggestion
+dotnet_style_explicit_tuple_names = true:suggestion
+dotnet_style_null_propagation = true:suggestion
+dotnet_style_object_initializer = true:suggestion
+dotnet_style_operator_placement_when_wrapping = beginning_of_line
+dotnet_style_prefer_auto_properties = true:silent
+dotnet_style_prefer_compound_assignment = true:suggestion
+dotnet_style_prefer_conditional_expression_over_assignment = true:silent
+dotnet_style_prefer_conditional_expression_over_return = true:silent
+dotnet_style_prefer_inferred_anonymous_type_member_names = true:suggestion
+dotnet_style_prefer_inferred_tuple_names = true:suggestion
+dotnet_style_prefer_is_null_check_over_reference_equality_method = true:suggestion
+dotnet_style_prefer_simplified_boolean_expressions = true:suggestion
+dotnet_style_prefer_simplified_interpolation = true:suggestion
+
+# Field preferences
+dotnet_style_readonly_field = true:suggestion
+
+# Parameter preferences
+dotnet_code_quality_unused_parameters = all:suggestion
+
+# Suppression preferences
+dotnet_remove_unnecessary_suppression_exclusions = none
+
+#### C# Coding Conventions ####
+
+# var preferences
+csharp_style_var_elsewhere = false:silent
+csharp_style_var_for_built_in_types = false:silent
+csharp_style_var_when_type_is_apparent = false:silent
+
+# Expression-bodied members
+csharp_style_expression_bodied_accessors = true:silent
+csharp_style_expression_bodied_constructors = false:silent
+csharp_style_expression_bodied_indexers = true:silent
+csharp_style_expression_bodied_lambdas = true:silent
+csharp_style_expression_bodied_local_functions = false:silent
+csharp_style_expression_bodied_methods = false:silent
+csharp_style_expression_bodied_operators = false:silent
+csharp_style_expression_bodied_properties = true:silent
+
+# Pattern matching preferences
+csharp_style_pattern_matching_over_as_with_null_check = true:suggestion
+csharp_style_pattern_matching_over_is_with_cast_check = true:suggestion
+csharp_style_prefer_not_pattern = true:suggestion
+csharp_style_prefer_pattern_matching = true:silent
+csharp_style_prefer_switch_expression = true:suggestion
+
+# Null-checking preferences
+csharp_style_conditional_delegate_call = true:suggestion
+
+# Modifier preferences
+csharp_prefer_static_local_function = true:suggestion
+csharp_preferred_modifier_order = public,private,protected,internal,static,extern,new,virtual,abstract,sealed,override,readonly,unsafe,volatile,async:silent
+
+# Code-block preferences
+csharp_prefer_braces = true:silent
+csharp_prefer_simple_using_statement = true:suggestion
+
+# Expression-level preferences
+csharp_prefer_simple_default_expression = true:suggestion
+csharp_style_deconstructed_variable_declaration = true:suggestion
+csharp_style_inlined_variable_declaration = true:suggestion
+csharp_style_pattern_local_over_anonymous_function = true:suggestion
+csharp_style_prefer_index_operator = true:suggestion
+csharp_style_prefer_range_operator = true:suggestion
+csharp_style_throw_expression = true:suggestion
+csharp_style_unused_value_assignment_preference = discard_variable:suggestion
+csharp_style_unused_value_expression_statement_preference = discard_variable:silent
+
+# 'using' directive preferences
+csharp_using_directive_placement = inside_namespace:silent
+
+#### C# Formatting Rules ####
+
+# New line preferences
+csharp_new_line_before_catch = false
+csharp_new_line_before_else = false
+csharp_new_line_before_finally = false
+csharp_new_line_before_members_in_anonymous_types = false
+csharp_new_line_before_members_in_object_initializers = false
+csharp_new_line_before_open_brace = none
+csharp_new_line_between_query_expression_clauses = true
+
+# Indentation preferences
+csharp_indent_block_contents = true
+csharp_indent_braces = false
+csharp_indent_case_contents = true
+csharp_indent_case_contents_when_block = true
+csharp_indent_labels = one_less_than_current
+csharp_indent_switch_labels = true
+
+# Space preferences
+csharp_space_after_cast = false
+csharp_space_after_colon_in_inheritance_clause = true
+csharp_space_after_comma = true
+csharp_space_after_dot = false
+csharp_space_after_keywords_in_control_flow_statements = true
+csharp_space_after_semicolon_in_for_statement = true
+csharp_space_around_binary_operators = before_and_after
+csharp_space_around_declaration_statements = false
+csharp_space_before_colon_in_inheritance_clause = true
+csharp_space_before_comma = false
+csharp_space_before_dot = false
+csharp_space_before_open_square_brackets = false
+csharp_space_before_semicolon_in_for_statement = false
+csharp_space_between_empty_square_brackets = false
+csharp_space_between_method_call_empty_parameter_list_parentheses = false
+csharp_space_between_method_call_name_and_opening_parenthesis = false
+csharp_space_between_method_call_parameter_list_parentheses = false
+csharp_space_between_method_declaration_empty_parameter_list_parentheses = false
+csharp_space_between_method_declaration_name_and_open_parenthesis = false
+csharp_space_between_method_declaration_parameter_list_parentheses = false
+csharp_space_between_parentheses = false
+csharp_space_between_square_brackets = false
+
+# Wrapping preferences
+csharp_preserve_single_line_blocks = true
+csharp_preserve_single_line_statements = true
+
+#### Naming styles ####
+
+# Naming rules
+
+dotnet_naming_rule.interface_should_be_begins_with_i.severity = suggestion
+dotnet_naming_rule.interface_should_be_begins_with_i.symbols = interface
+dotnet_naming_rule.interface_should_be_begins_with_i.style = begins_with_i
+
+dotnet_naming_rule.types_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.types_should_be_pascal_case.symbols = types
+dotnet_naming_rule.types_should_be_pascal_case.style = pascal_case
+
+dotnet_naming_rule.non_field_members_should_be_pascal_case.severity = suggestion
+dotnet_naming_rule.non_field_members_should_be_pascal_case.symbols = non_field_members
+dotnet_naming_rule.non_field_members_should_be_pascal_case.style = pascal_case
+
+# Symbol specifications
+
+dotnet_naming_symbols.interface.applicable_kinds = interface
+dotnet_naming_symbols.interface.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.interface.required_modifiers =
+
+dotnet_naming_symbols.types.applicable_kinds = class, struct, interface, enum
+dotnet_naming_symbols.types.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.types.required_modifiers =
+
+dotnet_naming_symbols.non_field_members.applicable_kinds = property, event, method
+dotnet_naming_symbols.non_field_members.applicable_accessibilities = public, internal, private, protected, protected_internal, private_protected
+dotnet_naming_symbols.non_field_members.required_modifiers =
+
+# Naming styles
+
+dotnet_naming_style.pascal_case.required_prefix =
+dotnet_naming_style.pascal_case.required_suffix =
+dotnet_naming_style.pascal_case.word_separator =
+dotnet_naming_style.pascal_case.capitalization = pascal_case
+
+dotnet_naming_style.begins_with_i.required_prefix = I
+dotnet_naming_style.begins_with_i.required_suffix =
+dotnet_naming_style.begins_with_i.word_separator =
+dotnet_naming_style.begins_with_i.capitalization = pascal_case

files/ib002/graphs/iterative-and-iterators/.gitignore

@@ -0,0 +1,448 @@
+## Ignore Visual Studio temporary files, build results, and
+## files generated by popular Visual Studio add-ons.
+##
+## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
+
+# User-specific files
+*.rsuser
+*.suo
+*.user
+*.userosscache
+*.sln.docstates
+
+# User-specific files (MonoDevelop/Xamarin Studio)
+*.userprefs
+
+# Mono auto generated files
+mono_crash.*
+
+# Build results
+[Dd]ebug/
+[Dd]ebugPublic/
+[Rr]elease/
+[Rr]eleases/
+x64/
+x86/
+[Aa][Rr][Mm]/
+[Aa][Rr][Mm]64/
+bld/
+[Bb]in/
+[Oo]bj/
+[Ll]og/
+[Ll]ogs/
+
+# Visual Studio 2015/2017 cache/options directory
+.vs/
+# Uncomment if you have tasks that create the project's static files in wwwroot
+#wwwroot/
+
+# Visual Studio 2017 auto generated files
+Generated\ Files/
+
+# MSTest test Results
+[Tt]est[Rr]esult*/
+[Bb]uild[Ll]og.*
+
+# NUnit
+*.VisualState.xml
+TestResult.xml
+nunit-*.xml
+
+# Build Results of an ATL Project
+[Dd]ebugPS/
+[Rr]eleasePS/
+dlldata.c
+
+# Benchmark Results
+BenchmarkDotNet.Artifacts/
+
+# .NET Core
+project.lock.json
+project.fragment.lock.json
+artifacts/
+
+# Tye
+.tye/
+
+# StyleCop
+StyleCopReport.xml
+
+# Files built by Visual Studio
+*_i.c
+*_p.c
+*_h.h
+*.ilk
+*.meta
+*.obj
+*.iobj
+*.pch
+*.pdb
+*.ipdb
+*.pgc
+*.pgd
+*.rsp
+*.sbr
+*.tlb
+*.tli
+*.tlh
+*.tmp
+*.tmp_proj
+*_wpftmp.csproj
+*.log
+*.vspscc
+*.vssscc
+.builds
+*.pidb
+*.svclog
+*.scc
+
+# Chutzpah Test files
+_Chutzpah*
+
+# Visual C++ cache files
+ipch/
+*.aps
+*.ncb
+*.opendb
+*.opensdf
+*.sdf
+*.cachefile
+*.VC.db
+*.VC.VC.opendb
+
+# Visual Studio profiler
+*.psess
+*.vsp
+*.vspx
+*.sap
+
+# Visual Studio Trace Files
+*.e2e
+
+# TFS 2012 Local Workspace
+$tf/
+
+# Guidance Automation Toolkit
+*.gpState
+
+# ReSharper is a .NET coding add-in
+_ReSharper*/
+*.[Rr]e[Ss]harper
+*.DotSettings.user
+
+# TeamCity is a build add-in
+_TeamCity*
+
+# DotCover is a Code Coverage Tool
+*.dotCover
+
+# AxoCover is a Code Coverage Tool
+.axoCover/*
+!.axoCover/settings.json
+
+# Coverlet is a free, cross platform Code Coverage Tool
+coverage*[.json, .xml, .info]
+
+# Visual Studio code coverage results
+*.coverage
+*.coveragexml
+
+# NCrunch
+_NCrunch_*
+.*crunch*.local.xml
+nCrunchTemp_*
+
+# MightyMoose
+*.mm.*
+AutoTest.Net/
+
+# Web workbench (sass)
+.sass-cache/
+
+# Installshield output folder
+[Ee]xpress/
+
+# DocProject is a documentation generator add-in
+DocProject/buildhelp/
+DocProject/Help/*.HxT
+DocProject/Help/*.HxC
+DocProject/Help/*.hhc
+DocProject/Help/*.hhk
+DocProject/Help/*.hhp
+DocProject/Help/Html2
+DocProject/Help/html
+
+# Click-Once directory
+publish/
+
+# Publish Web Output
+*.[Pp]ublish.xml
+*.azurePubxml
+# Note: Comment the next line if you want to checkin your web deploy settings,
+# but database connection strings (with potential passwords) will be unencrypted
+*.pubxml
+*.publishproj
+
+# Microsoft Azure Web App publish settings. Comment the next line if you want to
+# checkin your Azure Web App publish settings, but sensitive information contained
+# in these scripts will be unencrypted
+PublishScripts/
+
+# NuGet Packages
+*.nupkg
+# NuGet Symbol Packages
+*.snupkg
+# The packages folder can be ignored because of Package Restore
+**/[Pp]ackages/*
+# except build/, which is used as an MSBuild target.
+!**/[Pp]ackages/build/
+# Uncomment if necessary however generally it will be regenerated when needed
+#!**/[Pp]ackages/repositories.config
+# NuGet v3's project.json files produces more ignorable files
+*.nuget.props
+*.nuget.targets
+
+# Microsoft Azure Build Output
+csx/
+*.build.csdef
+
+# Microsoft Azure Emulator
+ecf/
+rcf/
+
+# Windows Store app package directories and files
+AppPackages/
+BundleArtifacts/
+Package.StoreAssociation.xml
+_pkginfo.txt
+*.appx
+*.appxbundle
+*.appxupload
+
+# Visual Studio cache files
+# files ending in .cache can be ignored
+*.[Cc]ache
+# but keep track of directories ending in .cache
+!?*.[Cc]ache/
+
+# Others
+ClientBin/
+~$*
+*~
+*.dbmdl
+*.dbproj.schemaview
+*.jfm
+*.pfx
+*.publishsettings
+orleans.codegen.cs
+
+# Including strong name files can present a security risk
+# (https://github.com/github/gitignore/pull/2483#issue-259490424)
+#*.snk
+
+# Since there are multiple workflows, uncomment next line to ignore bower_components
+# (https://github.com/github/gitignore/pull/1529#issuecomment-104372622)
+#bower_components/
+
+# RIA/Silverlight projects
+Generated_Code/
+
+# Backup & report files from converting an old project file
+# to a newer Visual Studio version. Backup files are not needed,
+# because we have git ;-)
+_UpgradeReport_Files/
+Backup*/
+UpgradeLog*.XML
+UpgradeLog*.htm
+ServiceFabricBackup/
+*.rptproj.bak
+
+# SQL Server files
+*.mdf
+*.ldf
+*.ndf
+
+# Business Intelligence projects
+*.rdl.data
+*.bim.layout
+*.bim_*.settings
+*.rptproj.rsuser
+*- [Bb]ackup.rdl
+*- [Bb]ackup ([0-9]).rdl
+*- [Bb]ackup ([0-9][0-9]).rdl
+
+# Microsoft Fakes
+FakesAssemblies/
+
+# GhostDoc plugin setting file
+*.GhostDoc.xml
+
+# Node.js Tools for Visual Studio
+.ntvs_analysis.dat
+node_modules/
+
+# Visual Studio 6 build log
+*.plg
+
+# Visual Studio 6 workspace options file
+*.opt
+
+# Visual Studio 6 auto-generated workspace file (contains which files were open etc.)
+*.vbw
+
+# Visual Studio LightSwitch build output
+**/*.HTMLClient/GeneratedArtifacts
+**/*.DesktopClient/GeneratedArtifacts
+**/*.DesktopClient/ModelManifest.xml
+**/*.Server/GeneratedArtifacts
+**/*.Server/ModelManifest.xml
+_Pvt_Extensions
+
+# Paket dependency manager
+.paket/paket.exe
+paket-files/
+
+# FAKE - F# Make
+.fake/
+
+# Ionide - VsCode extension for F# Support
+.ionide/
+
+# CodeRush personal settings
+.cr/personal
+
+# Python Tools for Visual Studio (PTVS)
+__pycache__/
+*.pyc
+
+# Cake - Uncomment if you are using it
+# tools/**
+# !tools/packages.config
+
+# Tabs Studio
+*.tss
+
+# Telerik's JustMock configuration file
+*.jmconfig
+
+# BizTalk build output
+*.btp.cs
+*.btm.cs
+*.odx.cs
+*.xsd.cs
+
+# OpenCover UI analysis results
+OpenCover/
+
+# Azure Stream Analytics local run output
+ASALocalRun/
+
+# MSBuild Binary and Structured Log
+*.binlog
+
+# NVidia Nsight GPU debugger configuration file
+*.nvuser
+
+# MFractors (Xamarin productivity tool) working folder
+.mfractor/
+
+# Local History for Visual Studio
+.localhistory/
+
+# BeatPulse healthcheck temp database
+healthchecksdb
+
+# Backup folder for Package Reference Convert tool in Visual Studio 2017
+MigrationBackup/
+
+# Ionide (cross platform F# VS Code tools) working folder
+.ionide/
+
+##
+## Visual studio for Mac
+##
+
+
+# globs
+Makefile.in
+*.userprefs
+*.usertasks
+config.make
+config.status
+aclocal.m4
+install-sh
+autom4te.cache/
+*.tar.gz
+tarballs/
+test-results/
+
+# Mac bundle stuff
+*.dmg
+*.app
+
+# content below from: https://github.com/github/gitignore/blob/master/Global/macOS.gitignore
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+# content below from: https://github.com/github/gitignore/blob/master/Global/Windows.gitignore
+# Windows thumbnail cache files
+Thumbs.db
+ehthumbs.db
+ehthumbs_vista.db
+
+# Dump file
+*.stackdump
+
+# Folder config file
+[Dd]esktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+
+# JetBrains Rider
+.idea/
+*.sln.iml
+
+##
+## Visual Studio Code
+##
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json

files/ib002/graphs/iterative-and-iterators/graphs.csproj

@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

files/ib002/graphs/iterative-and-iterators/src/BFS.cs

@@ -0,0 +1,66 @@
+using System.Collections.Generic;
+
+namespace graphs {
+    class BFS<T> where T : notnull {
+        private Graph<T> graph;
+
+        private Dictionary<T, int> Distance = new Dictionary<T, int>();
+        private Dictionary<T, T?> Parent = new Dictionary<T, T?>();
+        private Dictionary<T, Color> State = new Dictionary<T, Color>();
+
+        public BFS(Graph<T> graph) {
+            this.graph = graph;
+        }
+
+        public BFS<T> Run() {
+            foreach (var vertex in graph.Vertices) {
+                if (ColorOf(vertex) == Color.White) {
+                    RunFrom(vertex);
+                }
+            }
+
+            return this;
+        }
+
+        public BFS<T> RunFrom(T start) {
+            State[start] = Color.Gray;
+            Distance[start] = 0;
+            Parent[start] = default(T);
+
+            var queue = new Queue<T>();
+            queue.Enqueue(start);
+
+            while (queue.Count > 0) {
+                var u = queue.Dequeue();
+
+                for (var iterator = graph.GetEdgesFrom(u); iterator.MoveNext();) {
+                    var v = iterator.Current;
+
+                    if (GetOrDefault(State, v, Color.White) == Color.White) {
+                        State[v] = Color.Gray;
+                        Distance[v] = Distance[u] + 1;
+                        Parent[v] = u;
+
+                        queue.Enqueue(v);
+                    }
+                }
+
+                State[u] = Color.Black;
+            }
+
+            return this;
+        }
+
+        private static V GetOrDefault<U, V>(Dictionary<U, V> flags, U u, V defaultValue)
+            where U : notnull {
+            if (flags.TryGetValue(u, out var flag)) {
+                return flag;
+            }
+            return defaultValue;
+        }
+
+        public int DistanceTo(T u) => GetOrDefault(Distance, u, 0);
+        public T? ParentOf(T u) => GetOrDefault(Parent, u, default(T));
+        public Color ColorOf(T u) => GetOrDefault(State, u, Color.White);
+    }
+}

files/ib002/graphs/iterative-and-iterators/src/DFS.cs

@@ -0,0 +1,68 @@
+using System.Collections.Generic;
+
+namespace graphs {
+    class DFS<T> where T : notnull {
+        private Graph<T> graph;
+
+        private int time;
+        private Dictionary<T, int> Discovered = new Dictionary<T, int>();
+        private Dictionary<T, int> Finished = new Dictionary<T, int>();
+        private Dictionary<T, Color> State = new Dictionary<T, Color>();
+
+        public DFS(Graph<T> graph) {
+            this.graph = graph;
+        }
+
+        public DFS<T> Run() {
+            time = 0;
+
+            foreach (var vertex in graph.Vertices) {
+                if (ColorOf(vertex) == Color.White) {
+                    RunFrom(vertex, false);
+                }
+            }
+
+            return this;
+        }
+
+        public DFS<T> RunFrom(T start, bool reset = true) {
+            var path = new Stack<(T, IEnumerator<T>)>();
+
+            if (reset) {
+                time = 0;
+            }
+
+            (Discovered[start], State[start]) = (++time, Color.Gray);
+            path.Push((start, graph.GetEdgesFrom(start)));
+
+            while (path.Count > 0) {
+                var (lastVertex, successors) = path.Peek();
+
+                if (!successors.MoveNext()) {
+                    path.Pop();
+                    (Finished[lastVertex], State[lastVertex]) = (++time, Color.Black);
+                } else if (ColorOf(successors.Current) == Color.White) {
+                    var nextVertex = successors.Current;
+
+                    (Discovered[nextVertex], State[nextVertex]) = (++time, Color.Gray);
+                    path.Push((nextVertex, graph.GetEdgesFrom(nextVertex)));
+                }
+            }
+
+            return this;
+        }
+
+        private static V GetOrDefault<U, V>(Dictionary<U, V> flags, U u, V defaultValue)
+            where U : notnull
+            where V : notnull {
+            if (flags.TryGetValue(u, out var flag)) {
+                return flag;
+            }
+            return defaultValue;
+        }
+
+        public int DiscoveredAt(T u) => GetOrDefault(Discovered, u, 0);
+        public int FinishedAt(T u) => GetOrDefault(Finished, u, 0);
+        public Color ColorOf(T u) => GetOrDefault(State, u, Color.White);
+    }
+}

files/ib002/graphs/iterative-and-iterators/src/Graph.cs

@@ -0,0 +1,44 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace graphs {
+    enum Color {
+        White, Gray, Black
+    }
+
+    class Graph<T> where T : notnull {
+        private SortedSet<T> vertices = new SortedSet<T>();
+        private SortedDictionary<T, SortedSet<T>> edges = new SortedDictionary<T, SortedSet<T>>();
+
+        public SortedSet<T> Vertices {
+            get => vertices;
+        }
+
+        public void AddVertex(T u) {
+            vertices.Add(u);
+            edges.Add(u, new SortedSet<T>());
+        }
+
+        public void AddEdge(T u, T v) {
+            if (edges.TryGetValue(u, out var edgesFromU)) {
+                edgesFromU.Add(v);
+            }
+        }
+
+        public bool HasEdge(T u, T v) {
+            if (edges.TryGetValue(u, out var edgesFromU)) {
+                return edgesFromU.Contains(v);
+            }
+
+            return false;
+        }
+
+        public IEnumerator<T> GetEdgesFrom(T u) {
+            if (edges.TryGetValue(u, out var edgesFromU)) {
+                return edgesFromU.GetEnumerator();
+            }
+
+            return Enumerable.Empty<T>().GetEnumerator();
+        }
+    }
+}

files/ib002/graphs/iterative-and-iterators/src/Program.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+
+namespace graphs {
+    class Program {
+        static Graph<string> CreateExampleGraph() {
+            var vertices = new List<string>() {
+                "s", "q", "t", "y", "r", "v", "w", "x", "z", "u"
+            };
+
+            var graph = new Graph<string>();
+
+            foreach (var vertex in vertices) {
+                graph.AddVertex(vertex);
+            }
+
+            graph.AddEdge("s", "v");
+            graph.AddEdge("q", "s");
+            graph.AddEdge("q", "w");
+            graph.AddEdge("q", "t");
+            graph.AddEdge("t", "y");
+            graph.AddEdge("t", "x");
+            graph.AddEdge("y", "q");
+            graph.AddEdge("r", "y");
+            graph.AddEdge("r", "u");
+            graph.AddEdge("v", "w");
+            graph.AddEdge("w", "s");
+            graph.AddEdge("x", "w");
+            graph.AddEdge("x", "z");
+            graph.AddEdge("z", "x");
+            graph.AddEdge("u", "y");
+
+            return graph;
+        }
+
+        static void Main(string[] args) {
+            var graph = CreateExampleGraph();
+
+            var dfsTraversal = new DFS<string>(graph).Run();
+            foreach (var vertex in graph.Vertices) {
+                Console.WriteLine($"{vertex}(d: {dfsTraversal.DiscoveredAt(vertex)}, f: {dfsTraversal.FinishedAt(vertex)})");
+            }
+        }
+    }
+}

files/ib002/rb-trees/rules/rb.dot

@@ -0,0 +1,47 @@
+digraph {
+    "Node(value=3, rank=2)" [label="3"]; #done
+    "Node(value=1, rank=1)" [label="1"]; #done
+    "Node(value=4, rank=0)" [label="4"]; #done
+    "Node(value=7, rank=1)" [label="7", color="red"]; #done
+    "Node(value=0, rank=0)" [label="0"]; #done
+    "Node(value=2, rank=0)" [label="2"]; #done
+    "Node(value=5, rank=1)" [label="5"]; #done
+    "Node(value=6, rank=0)" [label="6"]; #done
+    "Node(value=8, rank=0)" [label="8"]; #done
+
+    "nil1" [label="nil"]
+    "nil2" [label="nil"]
+    "nil3" [label="nil"]
+    "nil4" [label="nil"]
+    "nil5" [label="nil"]
+    "nil6" [label="nil"]
+    "nil7" [label="nil"]
+    "nil8" [label="nil"]
+    "nil9" [label="nil"]
+    "nil10" [label="nil"]
+    "nil11" [label="nil"]
+    "Node(value=9, rank=0)" [label="9", color="red"]; #done
+
+    "Node(value=3, rank=2)" -> "Node(value=1, rank=1)" #done
+    "Node(value=1, rank=1)" -> "Node(value=0, rank=0)" #done
+    "Node(value=1, rank=1)" -> "Node(value=2, rank=0)" #done
+    "Node(value=3, rank=2)" -> "Node(value=5, rank=1)" #done
+    "Node(value=5, rank=1)" -> "Node(value=4, rank=0)" #done
+    "Node(value=5, rank=1)" -> "Node(value=7, rank=1)" [color="red"] #done
+    "Node(value=7, rank=1)" -> "Node(value=6, rank=0)" #done
+    "Node(value=7, rank=1)" -> "Node(value=8, rank=0)" #done
+
+    "Node(value=8, rank=0)" -> "nil1"
+    "Node(value=8, rank=0)" -> "Node(value=9, rank=0)" [color="red"] #done
+
+    "Node(value=0, rank=0)" -> "nil2"
+    "Node(value=0, rank=0)" -> "nil3"
+    "Node(value=2, rank=0)" -> "nil4"
+    "Node(value=2, rank=0)" -> "nil5"
+    "Node(value=4, rank=0)" -> "nil6"
+    "Node(value=4, rank=0)" -> "nil7"
+    "Node(value=6, rank=0)" -> "nil8"
+    "Node(value=6, rank=0)" -> "nil9"
+    "Node(value=9, rank=0)" -> "nil10"
+    "Node(value=9, rank=0)" -> "nil11"
+}

files/ib002/rb-trees/rules/rb_height.dot

@@ -0,0 +1,47 @@
+digraph {
+    "Node(value=3, rank=2)" [label="3⁽³⁾"]; #done
+    "Node(value=1, rank=1)" [label="1⁽²⁾"]; #done
+    "Node(value=4, rank=0)" [label="4⁽¹⁾"]; #done
+    "Node(value=7, rank=1)" [label="7⁽²⁾", color="red"]; #done
+    "Node(value=0, rank=0)" [label="0⁽¹⁾"]; #done
+    "Node(value=2, rank=0)" [label="2⁽¹⁾"]; #done
+    "Node(value=5, rank=1)" [label="5⁽²⁾"]; #done
+    "Node(value=6, rank=0)" [label="6⁽¹⁾"]; #done
+    "Node(value=8, rank=0)" [label="8⁽¹⁾"]; #done
+
+    "nil1" [label="nil"]
+    "nil2" [label="nil"]
+    "nil3" [label="nil"]
+    "nil4" [label="nil"]
+    "nil5" [label="nil"]
+    "nil6" [label="nil"]
+    "nil7" [label="nil"]
+    "nil8" [label="nil"]
+    "nil9" [label="nil"]
+    "nil10" [label="nil"]
+    "nil11" [label="nil"]
+    "Node(value=9, rank=0)" [label="9⁽¹⁾", color="red"]; #done
+
+    "Node(value=3, rank=2)" -> "Node(value=1, rank=1)" #done
+    "Node(value=1, rank=1)" -> "Node(value=0, rank=0)" #done
+    "Node(value=1, rank=1)" -> "Node(value=2, rank=0)" #done
+    "Node(value=3, rank=2)" -> "Node(value=5, rank=1)" #done
+    "Node(value=5, rank=1)" -> "Node(value=4, rank=0)" #done
+    "Node(value=5, rank=1)" -> "Node(value=7, rank=1)" [color="red"] #done
+    "Node(value=7, rank=1)" -> "Node(value=6, rank=0)" #done
+    "Node(value=7, rank=1)" -> "Node(value=8, rank=0)" #done
+
+    "Node(value=8, rank=0)" -> "nil1"
+    "Node(value=8, rank=0)" -> "Node(value=9, rank=0)" [color="red"] #done
+
+    "Node(value=0, rank=0)" -> "nil2"
+    "Node(value=0, rank=0)" -> "nil3"
+    "Node(value=2, rank=0)" -> "nil4"
+    "Node(value=2, rank=0)" -> "nil5"
+    "Node(value=4, rank=0)" -> "nil6"
+    "Node(value=4, rank=0)" -> "nil7"
+    "Node(value=6, rank=0)" -> "nil8"
+    "Node(value=6, rank=0)" -> "nil9"
+    "Node(value=9, rank=0)" -> "nil10"
+    "Node(value=9, rank=0)" -> "nil11"
+}

files/ib002/rb-trees/rules/red-node-black-children/correct.dot

@@ -0,0 +1,34 @@
+digraph {
+    "Node(value=3, rank=2)" [label="3"]; #done
+    "Node(value=1, rank=1)" [label="1", color="red"]; #done
+    "Node(value=4, rank=0)" [label="4", color="red"]; #done
+    "Node(value=7, rank=0)" [label="7", color="red"]; #done
+    "Node(value=0, rank=0)" [label="0"]; #done
+    "Node(value=2, rank=0)" [label="2"]; #done
+    "Node(value=5, rank=1)" [label="5"]; #done
+
+    "nil2" [label="", color=none]
+    "nil3" [label="", color=none]
+    "nil4" [label="", color=none]
+    "nil5" [label="", color=none]
+    "nil6" [label="", color=none]
+    "nil7" [label="", color=none]
+    "nil8" [label="", color=none]
+    "nil9" [label="", color=none]
+
+    "Node(value=3, rank=2)" -> "Node(value=1, rank=1)" #done
+    "Node(value=1, rank=1)" -> "Node(value=0, rank=0)" #done
+    "Node(value=1, rank=1)" -> "Node(value=2, rank=0)" #done
+    "Node(value=3, rank=2)" -> "Node(value=5, rank=1)" #done
+    "Node(value=5, rank=1)" -> "Node(value=4, rank=0)" #done
+    "Node(value=5, rank=1)" -> "Node(value=7, rank=0)" [color="red"] #done
+
+    "Node(value=0, rank=0)" -> "nil2"
+    "Node(value=0, rank=0)" -> "nil3"
+    "Node(value=2, rank=0)" -> "nil4"
+    "Node(value=2, rank=0)" -> "nil5"
+    "Node(value=4, rank=0)" -> "nil6"
+    "Node(value=4, rank=0)" -> "nil7"
+    "Node(value=7, rank=0)" -> "nil8"
+    "Node(value=7, rank=0)" -> "nil9"
+}

files/ib002/rb-trees/rules/red-node-black-children/incorrect.dot

@@ -0,0 +1,40 @@
+digraph {
+    "Node(value=3, rank=2)" [label="3"]; #done
+    "Node(value=1, rank=1)" [label="1", color="red"]; #done
+    "Node(value=4, rank=0)" [label="4", color="red"]; #done
+    "Node(value=7, rank=0)" [label="7", color="red"]; #done
+    "Node(value=0, rank=0)" [label="0"]; #done
+    "Node(value=2, rank=0)" [label="2"]; #done
+    "Node(value=5, rank=1)" [label="5"]; #done
+    
+
+    "nil2" [label="", color=none]
+    "nil3" [label="", color=none]
+    "nil4" [label="", color=none]
+    "nil5" [label="", color=none]
+    "nil6" [label="", color=none]
+    "nil7" [label="", color=none]
+    "nil8" [label="", color=none]
+    "nil9" [label="", color=none]
+    "nil10" [label="", color=none]
+    "8" [label="8", color="red"]
+
+    "Node(value=3, rank=2)" -> "Node(value=1, rank=1)" #done
+    "Node(value=1, rank=1)" -> "Node(value=0, rank=0)" #done
+    "Node(value=1, rank=1)" -> "Node(value=2, rank=0)" #done
+    "Node(value=3, rank=2)" -> "Node(value=5, rank=1)" #done
+    "Node(value=5, rank=1)" -> "Node(value=4, rank=0)" #done
+    "Node(value=5, rank=1)" -> "Node(value=7, rank=0)" [color="red"] #done
+
+    "Node(value=0, rank=0)" -> "nil2"
+    "Node(value=0, rank=0)" -> "nil3"
+    "Node(value=2, rank=0)" -> "nil4"
+    "Node(value=2, rank=0)" -> "nil5"
+    "Node(value=4, rank=0)" -> "nil6"
+    "Node(value=4, rank=0)" -> "nil7"
+    "Node(value=7, rank=0)" -> "nil8"
+    "Node(value=7, rank=0)" -> "8" [color="red"]
+    
+    "8" -> "nil9"
+    "8" -> "nil10"
+}

files/ib002/rb-trees/rules/red-root/br_0.dot

@@ -0,0 +1,7 @@
+digraph RBTree {
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+R140399805603280 [label="",color=none]
+140399805603280 -> R140399805603280
+}

files/ib002/rb-trees/rules/red-root/br_1.dot

@@ -0,0 +1,11 @@
+digraph RBTree {
+"140399805603280" [label="12"]
+"140399805603280" -> "140399804142928" [color="red"]
+"140399804142928" [color=red,label="5"]
+L140399804142928 [label="",color=none]
+140399804142928 -> L140399804142928
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+R140399805603280 [label="",color=none]
+140399805603280 -> R140399805603280
+}

files/ib002/rb-trees/rules/red-root/br_2.dot

@@ -0,0 +1,15 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928" [color="red"]
+"140399804142928" [color=red,label="5"]
+L140399804142928 [label="",color=none]
+140399804142928 -> L140399804142928
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805603280" [color="red"]
+"140399805603280" [color=red,label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+R140399805603280 [label="",color=none]
+140399805603280 -> R140399805603280
+}

files/ib002/rb-trees/rules/red-root/br_3.dot

@@ -0,0 +1,19 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+L140399804142928 [label="",color=none]
+140399804142928 -> L140399804142928
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805603280"
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+"140399805603280" -> "140399805700368" [color="red"]
+"140399805700368" [color=red,label="18"]
+L140399805700368 [label="",color=none]
+140399805700368 -> L140399805700368
+R140399805700368 [label="",color=none]
+140399805700368 -> R140399805700368
+}

files/ib002/rb-trees/rules/red-root/br_4.dot

@@ -0,0 +1,23 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+"140399804142928" -> "140399805700304" [color="red"]
+"140399805700304" [color=red,label="2"]
+L140399805700304 [label="",color=none]
+140399805700304 -> L140399805700304
+R140399805700304 [label="",color=none]
+140399805700304 -> R140399805700304
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805603280"
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+"140399805603280" -> "140399805700368" [color="red"]
+"140399805700368" [color=red,label="18"]
+L140399805700368 [label="",color=none]
+140399805700368 -> L140399805700368
+R140399805700368 [label="",color=none]
+140399805700368 -> R140399805700368
+}

files/ib002/rb-trees/rules/red-root/br_5.dot

@@ -0,0 +1,27 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+"140399804142928" -> "140399805700304" [color="red"]
+"140399805700304" [color=red,label="2"]
+L140399805700304 [label="",color=none]
+140399805700304 -> L140399805700304
+R140399805700304 [label="",color=none]
+140399805700304 -> R140399805700304
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805605392"
+"140399805605392" [label="15"]
+"140399805605392" -> "140399805603280" [color="red"]
+"140399805603280" [color=red,label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+R140399805603280 [label="",color=none]
+140399805603280 -> R140399805603280
+"140399805605392" -> "140399805700368" [color="red"]
+"140399805700368" [color=red,label="18"]
+L140399805700368 [label="",color=none]
+140399805700368 -> L140399805700368
+R140399805700368 [label="",color=none]
+140399805700368 -> R140399805700368
+}

files/ib002/rb-trees/rules/red-root/br_6.dot

@@ -0,0 +1,31 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+"140399804142928" -> "140399805700304" [color="red"]
+"140399805700304" [color=red,label="2"]
+L140399805700304 [label="",color=none]
+140399805700304 -> L140399805700304
+R140399805700304 [label="",color=none]
+140399805700304 -> R140399805700304
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805605392" [color="red"]
+"140399805605392" [color=red,label="15"]
+"140399805605392" -> "140399805603280"
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+"140399805603280" -> "140399805605456" [color="red"]
+"140399805605456" [color=red,label="13"]
+L140399805605456 [label="",color=none]
+140399805605456 -> L140399805605456
+R140399805605456 [label="",color=none]
+140399805605456 -> R140399805605456
+"140399805605392" -> "140399805700368"
+"140399805700368" [label="18"]
+L140399805700368 [label="",color=none]
+140399805700368 -> L140399805700368
+R140399805700368 [label="",color=none]
+140399805700368 -> R140399805700368
+}

files/ib002/rb-trees/rules/red-root/br_7.dot

@@ -0,0 +1,35 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+"140399804142928" -> "140399805700304" [color="red"]
+"140399805700304" [color=red,label="2"]
+L140399805700304 [label="",color=none]
+140399805700304 -> L140399805700304
+R140399805700304 [label="",color=none]
+140399805700304 -> R140399805700304
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805605392" [color="red"]
+"140399805605392" [color=red,label="15"]
+"140399805605392" -> "140399805603280"
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+"140399805603280" -> "140399805605456" [color="red"]
+"140399805605456" [color=red,label="13"]
+L140399805605456 [label="",color=none]
+140399805605456 -> L140399805605456
+R140399805605456 [label="",color=none]
+140399805605456 -> R140399805605456
+"140399805605392" -> "140399805700368"
+"140399805700368" [label="18"]
+L140399805700368 [label="",color=none]
+140399805700368 -> L140399805700368
+"140399805700368" -> "140399805605584" [color="red"]
+"140399805605584" [color=red,label="19"]
+L140399805605584 [label="",color=none]
+140399805605584 -> L140399805605584
+R140399805605584 [label="",color=none]
+140399805605584 -> R140399805605584
+}

files/ib002/rb-trees/rules/red-root/br_8.dot

@@ -0,0 +1,39 @@
+digraph RBTree {
+"140399805910672" [label="9"]
+"140399805910672" -> "140399804142928"
+"140399804142928" [label="5"]
+"140399804142928" -> "140399805700304" [color="red"]
+"140399805700304" [color=red,label="2"]
+L140399805700304 [label="",color=none]
+140399805700304 -> L140399805700304
+R140399805700304 [label="",color=none]
+140399805700304 -> R140399805700304
+R140399804142928 [label="",color=none]
+140399804142928 -> R140399804142928
+"140399805910672" -> "140399805605392" [color="red"]
+"140399805605392" [color=red,label="15"]
+"140399805605392" -> "140399805603280"
+"140399805603280" [label="12"]
+L140399805603280 [label="",color=none]
+140399805603280 -> L140399805603280
+"140399805603280" -> "140399805605456" [color="red"]
+"140399805605456" [color=red,label="13"]
+L140399805605456 [label="",color=none]
+140399805605456 -> L140399805605456
+R140399805605456 [label="",color=none]
+140399805605456 -> R140399805605456
+"140399805605392" -> "140399805700368"
+"140399805700368" [label="18"]
+"140399805700368" -> "140399804318928" [color="red"]
+"140399804318928" [color=red,label="17"]
+L140399804318928 [label="",color=none]
+140399804318928 -> L140399804318928
+R140399804318928 [label="",color=none]
+140399804318928 -> R140399804318928
+"140399805700368" -> "140399805605584" [color="red"]
+"140399805605584" [color=red,label="19"]
+L140399805605584 [label="",color=none]
+140399805605584 -> L140399805605584
+R140399805605584 [label="",color=none]
+140399805605584 -> R140399805605584
+}

files/ib002/rb-trees/rules/red-root/rr_0.dot

@@ -0,0 +1,7 @@
+digraph RBTree {
+"139660435791312" [color=red,label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+R139660435791312 [label="",color=none]
+139660435791312 -> R139660435791312
+}

files/ib002/rb-trees/rules/red-root/rr_1.dot

@@ -0,0 +1,11 @@
+digraph RBTree {
+"139660435791312" [label="12"]
+"139660435791312" -> "139660436098128" [color="red"]
+"139660436098128" [color=red,label="5"]
+L139660436098128 [label="",color=none]
+139660436098128 -> L139660436098128
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+R139660435791312 [label="",color=none]
+139660435791312 -> R139660435791312
+}

files/ib002/rb-trees/rules/red-root/rr_2.dot

@@ -0,0 +1,15 @@
+digraph RBTree {
+"139660434247376" [label="9"]
+"139660434247376" -> "139660436098128" [color="red"]
+"139660436098128" [color=red,label="5"]
+L139660436098128 [label="",color=none]
+139660436098128 -> L139660436098128
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435791312" [color="red"]
+"139660435791312" [color=red,label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+R139660435791312 [label="",color=none]
+139660435791312 -> R139660435791312
+}

files/ib002/rb-trees/rules/red-root/rr_3.dot

@@ -0,0 +1,19 @@
+digraph RBTree {
+"139660434247376" [color=red,label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+L139660436098128 [label="",color=none]
+139660436098128 -> L139660436098128
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435791312"
+"139660435791312" [label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+"139660435791312" -> "139660435887824" [color="red"]
+"139660435887824" [color=red,label="18"]
+L139660435887824 [label="",color=none]
+139660435887824 -> L139660435887824
+R139660435887824 [label="",color=none]
+139660435887824 -> R139660435887824
+}

files/ib002/rb-trees/rules/red-root/rr_4.dot

@@ -0,0 +1,23 @@
+digraph RBTree {
+"139660434247376" [color=red,label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+"139660436098128" -> "139660435887760" [color="red"]
+"139660435887760" [color=red,label="2"]
+L139660435887760 [label="",color=none]
+139660435887760 -> L139660435887760
+R139660435887760 [label="",color=none]
+139660435887760 -> R139660435887760
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435791312"
+"139660435791312" [label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+"139660435791312" -> "139660435887824" [color="red"]
+"139660435887824" [color=red,label="18"]
+L139660435887824 [label="",color=none]
+139660435887824 -> L139660435887824
+R139660435887824 [label="",color=none]
+139660435887824 -> R139660435887824
+}

files/ib002/rb-trees/rules/red-root/rr_5.dot

@@ -0,0 +1,27 @@
+digraph RBTree {
+"139660434247376" [color=red,label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+"139660436098128" -> "139660435887760" [color="red"]
+"139660435887760" [color=red,label="2"]
+L139660435887760 [label="",color=none]
+139660435887760 -> L139660435887760
+R139660435887760 [label="",color=none]
+139660435887760 -> R139660435887760
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435793424"
+"139660435793424" [label="15"]
+"139660435793424" -> "139660435791312" [color="red"]
+"139660435791312" [color=red,label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+R139660435791312 [label="",color=none]
+139660435791312 -> R139660435791312
+"139660435793424" -> "139660435887824" [color="red"]
+"139660435887824" [color=red,label="18"]
+L139660435887824 [label="",color=none]
+139660435887824 -> L139660435887824
+R139660435887824 [label="",color=none]
+139660435887824 -> R139660435887824
+}

files/ib002/rb-trees/rules/red-root/rr_6.dot

@@ -0,0 +1,31 @@
+digraph RBTree {
+"139660434247376" [label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+"139660436098128" -> "139660435887760" [color="red"]
+"139660435887760" [color=red,label="2"]
+L139660435887760 [label="",color=none]
+139660435887760 -> L139660435887760
+R139660435887760 [label="",color=none]
+139660435887760 -> R139660435887760
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435793424" [color="red"]
+"139660435793424" [color=red,label="15"]
+"139660435793424" -> "139660435791312"
+"139660435791312" [label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+"139660435791312" -> "139660435793488" [color="red"]
+"139660435793488" [color=red,label="13"]
+L139660435793488 [label="",color=none]
+139660435793488 -> L139660435793488
+R139660435793488 [label="",color=none]
+139660435793488 -> R139660435793488
+"139660435793424" -> "139660435887824"
+"139660435887824" [label="18"]
+L139660435887824 [label="",color=none]
+139660435887824 -> L139660435887824
+R139660435887824 [label="",color=none]
+139660435887824 -> R139660435887824
+}

files/ib002/rb-trees/rules/red-root/rr_7.dot

@@ -0,0 +1,35 @@
+digraph RBTree {
+"139660434247376" [label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+"139660436098128" -> "139660435887760" [color="red"]
+"139660435887760" [color=red,label="2"]
+L139660435887760 [label="",color=none]
+139660435887760 -> L139660435887760
+R139660435887760 [label="",color=none]
+139660435887760 -> R139660435887760
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435793424" [color="red"]
+"139660435793424" [color=red,label="15"]
+"139660435793424" -> "139660435791312"
+"139660435791312" [label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+"139660435791312" -> "139660435793488" [color="red"]
+"139660435793488" [color=red,label="13"]
+L139660435793488 [label="",color=none]
+139660435793488 -> L139660435793488
+R139660435793488 [label="",color=none]
+139660435793488 -> R139660435793488
+"139660435793424" -> "139660435887824"
+"139660435887824" [label="18"]
+L139660435887824 [label="",color=none]
+139660435887824 -> L139660435887824
+"139660435887824" -> "139660435793616" [color="red"]
+"139660435793616" [color=red,label="19"]
+L139660435793616 [label="",color=none]
+139660435793616 -> L139660435793616
+R139660435793616 [label="",color=none]
+139660435793616 -> R139660435793616
+}

files/ib002/rb-trees/rules/red-root/rr_8.dot

@@ -0,0 +1,39 @@
+digraph RBTree {
+"139660434247376" [label="9"]
+"139660434247376" -> "139660436098128"
+"139660436098128" [label="5"]
+"139660436098128" -> "139660435887760" [color="red"]
+"139660435887760" [color=red,label="2"]
+L139660435887760 [label="",color=none]
+139660435887760 -> L139660435887760
+R139660435887760 [label="",color=none]
+139660435887760 -> R139660435887760
+R139660436098128 [label="",color=none]
+139660436098128 -> R139660436098128
+"139660434247376" -> "139660435793424" [color="red"]
+"139660435793424" [color=red,label="15"]
+"139660435793424" -> "139660435791312"
+"139660435791312" [label="12"]
+L139660435791312 [label="",color=none]
+139660435791312 -> L139660435791312
+"139660435791312" -> "139660435793488" [color="red"]
+"139660435793488" [color=red,label="13"]
+L139660435793488 [label="",color=none]
+139660435793488 -> L139660435793488
+R139660435793488 [label="",color=none]
+139660435793488 -> R139660435793488
+"139660435793424" -> "139660435887824"
+"139660435887824" [label="18"]
+"139660435887824" -> "139660434506512" [color="red"]
+"139660434506512" [color=red,label="17"]
+L139660434506512 [label="",color=none]
+139660434506512 -> L139660434506512
+R139660434506512 [label="",color=none]
+139660434506512 -> R139660434506512
+"139660435887824" -> "139660435793616" [color="red"]
+"139660435793616" [color=red,label="19"]
+L139660435793616 [label="",color=none]
+139660435793616 -> L139660435793616
+R139660435793616 [label="",color=none]
+139660435793616 -> R139660435793616
+}

files/ib002/recursion/karel-1/generate_mazes.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+
+from itertools import product
+
+
+def generate_map(template: str, st: int, ave: int) -> str:
+    return template.format(st=st, ave=ave)
+
+
+def main():
+    template = None
+    with open("maze_skel.kw", "r") as f:
+        template = f.read()
+
+    for st, ave in product(range(1, 7), range(1, 7)):
+        with open("maze{:03d}.kw".format(st * 6 + ave), "w") as out:
+            print(generate_map(template, st, ave), file=out)
+
+
+if __name__ == "__main__":
+    main()

files/ib002/recursion/karel-1/karel_tk.py

@@ -0,0 +1,791 @@
+from dataclasses import dataclass
+from enum import Enum, IntEnum
+from functools import wraps
+from itertools import product
+from math import radians, sin, cos
+from sys import stderr
+import tkinter as tk
+from typing import Tuple, Union
+
+
+def check_before(precondition):
+    """
+    Decorator for running methods before executing a method.
+
+    Args:
+        call_before: Function to be called before executing a method.
+
+    Returns:
+        Parametrized decorator that can be used to wrap method with the
+        `call_before`.
+    """
+
+    def parametrized(f):
+        @wraps(f)
+        def wrapper(self, *args, **kwargs):
+            if not precondition(self, *args, **kwargs, fn=f):
+                return
+            return f(self, *args, **kwargs)
+
+        return wrapper
+
+    return parametrized
+
+
+def after(call_after):
+    """
+    Decorator for running methods after executing a method.
+
+    Args:
+        call_after: Function to be called after executing a method.
+
+    Returns:
+        Parametrized decorator that can be used to wrap method with the
+        `call_after`.
+    """
+
+    def parametrized(f):
+        @wraps(f)
+        def wrapper(self, *args, **kwargs):
+            result = f(self, *args, **kwargs)
+            call_after(self, *args, **kwargs, fn=f)
+            return result
+
+        return wrapper
+
+    return parametrized
+
+
+def skip_for_summary(f):
+    """
+    Decorator used for skipping a function call if the Karel is running
+    in a summary mode.
+    """
+
+    @wraps(f)
+    def wrapper(self, *args, **kwargs):
+        if self.summary_mode:
+            return
+        return f(self, *args, **kwargs)
+
+    return wrapper
+
+
+class Block(IntEnum):
+    """
+    Represents a field in the world of the Robot Karel.
+    It can be either clear or a wall.
+    """
+
+    Clear = 0
+    Wall = -1
+
+
+# Constants for major angles
+EAST, NORTH, WEST, SOUTH = 0, 90, 180, 270
+
+
+# @dataclass(frozen=True, slots=True)
+@dataclass(frozen=True)
+class _Direction:
+    """
+    angle: Represents heading of the Robot Karel
+    """
+
+    angle: int
+
+    @property
+    def vector(self) -> Tuple[int, int]:
+        """
+        Get a direction vector in the current direction the robot is heading.
+
+        Returns:
+            Pair of ints, representing a vector of (dx, dy).
+        """
+        angle, x, y = radians(self.angle), 1, 0
+        return (
+            x * round(cos(angle)) - y * round(sin(angle)),
+            x * round(sin(angle)) + y * round(cos(angle)),
+        )
+
+    @property
+    def in_world(self) -> str:
+        """
+        Get a character that is being put in the graphical representation of
+        the Robot Karel.
+
+        Returns:
+            Character to be put in the world.
+        """
+        return {
+            Direction.East.value: ">",
+            Direction.North.value: "^",
+            Direction.West.value: "<",
+            Direction.South.value: "v",
+            # Direction.East.value: "⮞",
+            # Direction.North.value: "⮝",
+            # Direction.West.value: "⮜",
+            # Direction.South.value: "⮟",
+        }[self]
+
+    @property
+    def as_string(self) -> str:
+        """
+        Returns a string with a direction for Tk label.
+
+        Returns:
+            Label of the direction
+        """
+        return {
+            Direction.East.value: "east",
+            Direction.North.value: "north",
+            Direction.West.value: "west",
+            Direction.South.value: "south",
+        }[self]
+
+    def __add__(self, angle: int) -> "_Direction":
+        return _Direction((360 + self.angle + angle) % 360)
+
+
+class Direction(Enum):
+    """
+    Provides constants of directions Karel can face.
+    """
+
+    East = _Direction(EAST)
+    North = _Direction(NORTH)
+    West = _Direction(WEST)
+    South = _Direction(SOUTH)
+
+
+class KarelWindow:
+    def __init__(self, karel: "Karel", scale: int, font: str):
+        self.size = 32 * scale
+
+        self.steps = tk.Label(text=karel.steps, anchor="e")
+        self.steps.grid(row=0, column=0, sticky="e")
+
+        self.last_cmd = tk.Label(text=karel.last_command, anchor="w")
+        self.last_cmd.grid(row=0, column=1, columnspan=3, sticky="w")
+
+        tk.Label(text="CORNER").grid(row=1, column=0)
+        tk.Label(text="FACING").grid(row=1, column=1)
+        tk.Label(text="BEEP-BAG").grid(row=1, column=2)
+        tk.Label(text="BEEP-CORNER").grid(row=1, column=3)
+
+        self.corner = tk.Label()
+        self.corner.grid(row=2, column=0)
+
+        self.facing = tk.Label()
+        self.facing.grid(row=2, column=1)
+
+        self.beep_bag = tk.Label()
+        self.beep_bag.grid(row=2, column=2)
+
+        self.beep_corner = tk.Label()
+        self.beep_corner.grid(row=2, column=3)
+
+        self.canvas = tk.Canvas(
+            width=((karel.world.width + 1) // 2 + 2) * self.size,
+            height=((karel.world.height + 1) // 2 + 2) * self.size,
+            background="black",
+        )
+        self.canvas.grid(column=0, row=3, columnspan=4)
+
+        self.font = f"{font} {int(12 * scale)}"
+
+        self.__draw_world(karel.world)
+        self.render(karel)
+
+    def __draw_world(self, world: "World"):
+        m, n = (world.height + 1) // 2, (world.width + 1) // 2
+
+        # NUMBERS
+        self.canvas.create_text(
+            self.size // 2,
+            self.size,
+            text="ST.",
+            fill="white",
+            anchor="s",
+            font=self.font,
+        )
+        for i in range(m):
+            self.canvas.create_text(
+                self.size - 8,
+                (i + 2) * self.size - self.size // 2,
+                text=(m - i),
+                anchor="e",
+                fill="white",
+                font=self.font,
+            )
+        y = ((m + 1) * self.size) + 8
+        self.canvas.create_text(
+            (n + 1) * self.size + self.size // 2,
+            y,
+            text="AVE.",
+            fill="white",
+            anchor="n",
+            font=self.font,
+        )
+        for i in range(n):
+            self.canvas.create_text(
+                (i + 2) * self.size - self.size // 2,
+                y,
+                text=(i + 1),
+                anchor="n",
+                fill="white",
+                font=self.font,
+            )
+
+        # BORDER
+        self.canvas.create_rectangle(
+            self.size,
+            self.size,
+            self.size * (n + 1),
+            self.size * (m + 1),
+            fill="",
+            outline="white",
+        )
+
+        for row, col in product(range(world.height), range(world.width)):
+            block = world.data[row][col]
+            if row % 2 == 0 and col % 2 == 0:
+                self.__print_beeper(world, block or ".", row // 2, col // 2)
+            elif block == Block.Wall:
+                size = self.size
+                x = size + col // 2 * size
+                y = (world.width + 1) // 2 * size - row // 2 * size
+                if row % 2 == 1 and col % 2 == 0:
+                    self.canvas.create_line(x, y, x + size, y, fill="white")
+                elif row % 2 == 0:
+                    x += size
+                    self.canvas.create_line(x, y, x, y + size, fill="white")
+
+        self.canvas.update()
+
+    def __print_beeper(
+        self, world: "World", beeper: Union[str, int], row: int, column: int
+    ):
+        self.canvas.create_text(
+            (column + 1) * self.size + self.size // 2,
+            ((world.height + 1) // 2 - row) * self.size + self.size // 2,
+            text=str(beeper),
+            anchor="center",
+            fill="white",
+            font=self.font,
+        )
+
+    def render(self, karel: "Karel"):
+        self.facing["text"] = karel.direction.as_string
+
+        self.steps["text"] = karel.steps
+        self.last_cmd["text"] = karel.last_command
+        self.corner["text"] = f"({(karel.x + 2) // 2}, {(karel.y + 2) // 2})"
+        self.beep_bag["text"] = karel.beepers
+        self.beep_corner["text"] = karel.world.data[karel.y][karel.x]
+
+        i, j = (karel.y + 2) // 2, (karel.x + 2) // 2
+        size = self.size
+        x, y = j * size, ((karel.world.height + 1) // 2 - i + 1) * size
+        self.canvas.create_rectangle(
+            x + 1, y + 1, x + size - 1, y + size - 1, fill="black"
+        )
+
+        karel_on_map = karel.direction.in_world
+        self.canvas.create_text(
+            x + size // 2,
+            y + size // 2,
+            text=karel_on_map,
+            font=self.font + " bold",
+            fill="yellow",
+            anchor="center",
+        )
+
+        self.canvas.update()
+        self.canvas.after(karel.step_delay)
+
+    def update(self, karel: "Karel", dx: int, dy: int):
+        block = karel.world.data[karel.y - 2 * dy][karel.x - 2 * dx]
+
+        i, j = (karel.y - 2 * dy) // 2, (karel.x - 2 * dx) // 2
+        x, y = (j + 1) * self.size, (
+            (karel.world.height + 1) // 2 - i
+        ) * self.size
+
+        self.canvas.create_rectangle(
+            x + 1, y + 1, x + self.size - 1, y + self.size - 1, fill="black"
+        )
+        self.__print_beeper(karel.world, block or ".", i, j)
+
+    def error(self, karel: "Karel", message: str):
+        self.render(karel)
+
+        self.last_cmd["foreground"] = "red"
+        self.last_cmd["text"] = f"Error Shutoff! ({message})"
+
+
+class World:
+    def __init__(self, width, height, data):
+        self.width = width * 2 - 1
+        self.height = height * 2 - 1
+        self.data = [
+            [0 for _ in range(self.width)] for _ in range(self.height)
+        ]
+
+        if self.width > 30 or self.height > 30:
+            raise ValueError(
+                "The given world is greater than the max values of [{}x{}]".format(
+                    30, 30
+                )
+            )
+
+        self._parse_world(data)
+
+    def __parse_wall(self, column, row, orientation, line):
+        column = column * 2 - 2
+        row = row * 2 - 2
+
+        if column % 2 == 1 or row % 2 == 1:
+            raise ValueError("Wrong position of the wall")
+
+        if orientation == "E":
+            column += 1
+        elif orientation == "W":
+            column -= 1
+        elif orientation == "N":
+            row += 1
+        elif orientation == "S":
+            row -= 1
+        else:
+            raise ValueError(
+                "Unknown wall orientation '{}' on line {} in world file".format(
+                    orientation, line
+                )
+            )
+
+        self.data[row][column] = Block.Wall
+        if column % 2 == 1 and row % 2 == 0:
+            if row + 1 < self.height:
+                self.data[row + 1][column] = Block.Wall
+            if row - 1 >= 0:
+                self.data[row - 1][column] = Block.Wall
+        else:
+            if column + 1 < self.width:
+                self.data[row][column + 1] = Block.Wall
+            if column - 1 >= 0:
+                self.data[row][column - 1] = Block.Wall
+
+    def __parse_beepers(self, column, row, count):
+        column = column * 2 - 2
+        row = row * 2 - 2
+        self.data[row][column] = count
+
+    def _parse_world(self, world_content):
+        for i, line in enumerate(world_content, 1):
+            if not line:
+                continue
+
+            block, column, row, arg = [part.upper() for part in line.split()]
+            if block == "W":
+                self.__parse_wall(int(column), int(row), arg, i)
+            elif block == "B":
+                self.__parse_beepers(int(column), int(row), int(arg))
+            else:
+                raise ValueError(
+                    "Unknown block character '{}' on line {} in world file".format(
+                        block, i
+                    )
+                )
+
+
+class Karel:
+    def __init__(
+        self, filename, summary_mode=False, scale=1, font="monospace"
+    ):
+        """
+        Turn Karel on.
+
+        Args:
+            filename: Path to the file containing Karel's world and initial
+                settings.
+            summary_mode: Disable rendering of the Karel's world in the window.
+
+                Defaults to `False`.
+            scale: Change the scaling factor of the font used to render Karel's
+                world.
+
+                Defaults to `1`.
+            font: Change the default monospace font that is used to render the
+                world.
+
+                Defaults to `"monospace"`.
+        """
+        self.summary_mode = summary_mode
+
+        world_content = None
+        with open(filename) as world_file:
+            world_content = world_file.read()
+
+        first_line, world = world_content.split("\n", maxsplit=1)
+        width, height, x, y, direction, beepers = first_line.split()
+        direction = direction.upper()
+
+        self.world = World(int(width), int(height), world.split("\n"))
+        self.x, self.y = int(x) * 2 - 2, int(y) * 2 - 2
+
+        if direction == "S":
+            self.direction = Direction.South.value
+        elif direction == "W":
+            self.direction = Direction.West.value
+        elif direction == "E":
+            self.direction = Direction.East.value
+        elif direction == "N":
+            self.direction = Direction.North.value
+        else:
+            raise ValueError("Unknown Karel's direction")
+
+        self.beepers = int(beepers)
+
+        self.steps = 0
+        self.step_delay = 1000
+        self.is_running = True
+        self.last_command = "turn_on"
+
+        self._initialize_window(scale, font)
+
+    @skip_for_summary
+    def _initialize_window(self, scale, font):
+        """
+        Initializes a window where the Karel is drawn.
+        """
+        self._window = KarelWindow(self, scale, font)
+
+    @skip_for_summary
+    def __update(self, dx, dy):
+        """
+        Updates Karel's position in the window.
+
+        Args:
+            dx: Change along the horizontal axis.
+            dy: Change along the vertical axis.
+        """
+        self._window.update(self, dx, dy)
+
+    def __render(self, fn, *args, **kwargs):
+        """
+        Updates step counter and last command for Karel.
+        If the robot is not running in a summary mode, then the window
+        is rendered once again.
+        """
+        if not self.is_running:
+            return
+
+        self.steps += 1
+        self.last_command = fn.__name__
+
+        if not self.summary_mode:
+            self._window.render(self)
+
+    def __error(self, message):
+        """
+        Provides error handling.
+
+        Args:
+            message: Error message to be shown.
+        """
+        if not self.summary_mode:
+            self._window.error(self, message)
+            self.is_running = False
+        else:
+            print(f"Error Shutoff! ({message})", file=stderr)
+
+    @skip_for_summary
+    def __deinit(self):
+        tk.mainloop()
+
+    def __check_state(self, *args, **kwargs):
+        """
+        Assures that commands are not run while the robot is not running.
+
+        Robot is not running when error has occurred.
+        """
+        return self.is_running
+
+    @check_before(__check_state)
+    def beepers_in_bag(self):
+        """
+        Check if there are any beepers in the Karel's bag.
+
+        Returns:
+            `True` if there is at least one beeper in Karel's beeper bag,
+            `False` otherwise.
+        """
+        return self.beepers > 0
+
+    def no_beepers_in_bag(self):
+        """
+        Check if there are no beepers in the Karel's bag.
+
+        Returns:
+            `True` if there is no beeper in Karel's beeper bag, `False` otherwise.
+        """
+        return not self.beepers_in_bag()
+
+    @check_before(__check_state)
+    def front_is_clear(self):
+        """
+        Check if there is no wall in front of Karel.
+
+        Returns:
+            `True` if there is no obstacle in front of Karel, `False` otherwise.
+        """
+        dx, dy = self.direction.vector
+        if not (
+            0 <= self.x + dx < self.world.width
+            and 0 <= self.y + dy < self.world.height
+        ):
+            return False
+
+        if self.world.data[self.y + dy][self.x + dx] == Block.Wall:
+            return False
+
+        return True
+
+    def front_is_blocked(self):
+        """
+        Check if there is a wall in front of Karel.
+
+        Returns:
+            `True` if there is an obstacle in front of Karel, `False` otherwise.
+        """
+        return not self.front_is_clear()
+
+    @check_before(__check_state)
+    def __side_is_clear(self, d):
+        """
+        Helper function for determining whether the sides of Karel are clear.
+
+        Args:
+            d: Counterclockwise change in angle of Karel's heading.
+
+        Returns:
+            `True` if the side after applying the `d` counterclokwise turn
+            is clear, `False` otherwise.
+        """
+        original_direction = self.direction
+        self.direction = self.direction + d
+
+        is_clear = self.front_is_clear()
+        self.direction = original_direction
+
+        return is_clear
+
+    def left_is_clear(self):
+        """
+        Check if there is no wall to the left side of Karel.
+
+        Returns:
+            `True` if there is no obstacle to the left side of Karel,
+            `False` otherwise.
+        """
+        return self.__side_is_clear(90)
+
+    def left_is_blocked(self):
+        """
+        Check if there is a wall to the left side of Karel.
+
+        Returns:
+            `True` if there is an obstacle to the left side of Karel,
+            `False` otherwise.
+        """
+        return not self.left_is_clear()
+
+    def right_is_clear(self):
+        """
+        Check if there is no wall to the right side of Karel.
+
+        Returns:
+            `True` if there is no obstacle to the right side of Karel,
+            `False` otherwise.
+        """
+        return self.__side_is_clear(-90)
+
+    def right_is_blocked(self):
+        """
+        Check if there is a wall to the right side of Karel.
+
+        Returns:
+            `True` if there is an obstacle to the right side of Karel,
+            `False` otherwise.
+        """
+        return not self.right_is_clear()
+
+    @check_before(__check_state)
+    def facing_north(self):
+        """
+        Check if Karel is facing north.
+
+        Returns:
+            `True` if Karel is facing north, `False` otherwise.
+        """
+        return self.direction == Direction.North
+
+    def not_facing_north(self):
+        """
+        Check if Karel is »not« facing north.
+
+        Returns:
+            `True` if Karel is »not« facing north, `False` otherwise.
+        """
+        return not self.facing_north()
+
+    @check_before(__check_state)
+    def facing_south(self):
+        """
+        Check if Karel is facing south.
+
+        Returns:
+            `True` if Karel is facing south, `False` otherwise.
+        """
+        return self.direction == Direction.South
+
+    def not_facing_south(self):
+        """
+        Check if Karel is »not« facing south.
+
+        Returns:
+            `True` if Karel is »not« facing south, `False` otherwise.
+        """
+        return not self.facing_south()
+
+    @check_before(__check_state)
+    def facing_east(self):
+        """
+        Check if Karel is facing east.
+
+        Returns:
+            `True` if Karel is facing east, `False` otherwise.
+        """
+        return self.direction == Direction.East
+
+    def not_facing_east(self):
+        """
+        Check if Karel is »not« facing east.
+
+        Returns:
+            `True` if Karel is »not« facing east, `False` otherwise.
+        """
+        return not self.facing_east()
+
+    @check_before(__check_state)
+    def facing_west(self):
+        """
+        Check if Karel is facing west.
+
+        Returns:
+            `True` if Karel is facing west, `False` otherwise.
+        """
+        return self.direction == Direction.West
+
+    def not_facing_west(self):
+        """
+        Check if Karel is »not« facing west.
+
+        Returns:
+            `True` if Karel is »not« facing west, `False` otherwise.
+        """
+        return not self.facing_west()
+
+    @check_before(__check_state)
+    def beepers_present(self):
+        """
+        Check whether Karel stands on a position that has any beepers present.
+
+        Returns:
+            `True` if there is at least one beeper present on the current
+            position, `False` otherwise.
+        """
+        return self.world.data[self.y][self.x] > 0
+
+    def no_beepers_present(self):
+        """
+        Check whether Karel stands on a position that has no beepers present.
+
+        Returns:
+            `True` if there is no beeper present on the current position,
+            `False` otherwise.
+        """
+        return not self.beepers_present()
+
+    @check_before(__check_state)
+    @after(__render)
+    def step(self):
+        """
+        Move Karel one position in the direction he's facing.
+        """
+        if not self.front_is_clear():
+            return self.__error("Can't move this way")
+
+        dx, dy = self.direction.vector
+        self.x += 2 * dx
+        self.y += 2 * dy
+        self.__update(dx, dy)
+
+    @check_before(__check_state)
+    @after(__render)
+    def turn_left(self):
+        """
+        Turn Karel counterclockwise, i.e. left, by 90 degrees.
+        """
+        self.direction = self.direction + 90
+
+    @after(__render)
+    def turn_off(self):
+        """
+        Turn Karel off.
+        """
+        self.is_running = False
+        self.__deinit()
+
+    @check_before(__check_state)
+    @after(__render)
+    def put_beeper(self):
+        """
+        Take a beeper from Karel's beeper bag and put on the current position.
+        """
+        if self.beepers <= 0:
+            return self.__error("Karel has no beeper to put at the corner")
+
+        self.world.data[self.y][self.x] += 1
+        self.beepers -= 1
+
+    @check_before(__check_state)
+    @after(__render)
+    def pick_beeper(self):
+        """
+        Pick a beeper from the current position and put it into Karel's
+        beeper bag.
+        """
+        if self.world.data[self.y][self.x] <= 0:
+            return self.__error("There is no beeper at the corner")
+
+        self.world.data[self.y][self.x] -= 1
+        self.beepers += 1
+
+    def set_step_delay(self, delay):
+        """
+        Set delay of a Karel's step.
+
+        Args:
+            delay: Delay of one step in milliseconds.
+        """
+        self.step_delay = delay
+
+    def get_step_delay(self):
+        """
+        Get current delay of a Karel's step.
+
+        Returns:
+            Current delay in milliseconds.
+        """
+        return self.step_delay

files/ib002/recursion/karel-1/maze007.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 1 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze008.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 2 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze009.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 3 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze010.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 4 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze011.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 5 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze012.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 1 6 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze013.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 2 1 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N

files/ib002/recursion/karel-1/maze014.kw

@@ -0,0 +1,34 @@
+6 6 1 1 E 72
+
+B 2 2 1
+
+W 1 1 E
+W 1 3 E
+W 1 4 E
+W 1 5 N
+
+W 2 1 N
+W 2 2 E
+W 2 2 N
+W 2 4 N
+W 2 5 E
+
+W 3 2 N
+W 3 3 N
+W 3 4 E
+W 3 5 E
+
+W 4 1 E
+W 4 1 N
+W 4 3 E
+W 4 3 N
+W 4 4 E
+W 4 5 E
+
+W 5 2 E
+W 5 2 N
+W 5 4 E
+W 5 5 N
+W 5 6 E
+
+W 6 4 N