From 0bb6581d69e51548c8bd671e6b8718bf8cb886bd Mon Sep 17 00:00:00 2001
From: Matej Focko <mfocko@redhat.com>
Date: Sun, 4 Sep 2022 23:02:44 +0200
Subject: [PATCH] =?UTF-8?q?problems(cpp):=20add=20=E2=80=9E987.=20Vertical?=
 =?UTF-8?q?=20Order=20Traversal=20of=20a=20Binary=20Tree=E2=80=9C?=
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Signed-off-by: Matej Focko <mfocko@redhat.com>
---
 ...tical-order-traversal-of-a-binary-tree.cpp | 243 ++++++++++++++++++
 1 file changed, 243 insertions(+)
 create mode 100644 problems/vertical-order-traversal-of-a-binary-tree.cpp

diff --git a/problems/vertical-order-traversal-of-a-binary-tree.cpp b/problems/vertical-order-traversal-of-a-binary-tree.cpp
new file mode 100644
index 0000000..6cd1ecc
--- /dev/null
+++ b/problems/vertical-order-traversal-of-a-binary-tree.cpp
@@ -0,0 +1,243 @@
+#include <deque>
+#include <map>
+#include <vector>
+
+// Definition for a binary tree node.
+struct TreeNode {
+    int val;
+    TreeNode* left;
+    TreeNode* right;
+    TreeNode()
+        : val(0)
+        , left(nullptr)
+        , right(nullptr)
+    {
+    }
+    TreeNode(int x)
+        : val(x)
+        , left(nullptr)
+        , right(nullptr)
+    {
+    }
+    TreeNode(int x, TreeNode* left, TreeNode* right)
+        : val(x)
+        , left(left)
+        , right(right)
+    {
+    }
+};
+
+namespace {
+
+struct TreeNodeHandle {
+    TreeNode* node;
+    int x;
+    int y;
+
+    TreeNodeHandle(TreeNode* node, int x, int y)
+        : node(node)
+        , x(x)
+        , y(y)
+    {
+    }
+
+    bool operator==(const TreeNodeHandle& rhs) const
+    {
+        return node == rhs.node && x == rhs.x && y == rhs.y;
+    }
+
+    int value() const
+    {
+        return node->val;
+    }
+
+    bool operator<(const TreeNodeHandle& rhs) const
+    {
+        if (y != rhs.y) {
+            return y < rhs.y;
+        }
+
+        if (x != rhs.x) {
+            return x < rhs.x;
+        }
+
+        return value() < rhs.value();
+    }
+};
+
+class verticals {
+    TreeNode* root;
+
+    class verticals_iter {
+        std::deque<TreeNodeHandle> queue;
+
+        void advance()
+        {
+            auto& n = queue.front();
+
+            if (n.node->left != nullptr) {
+                queue.push_back(TreeNodeHandle(n.node->left, n.x - 1, n.y + 1));
+            }
+
+            if (n.node->right != nullptr) {
+                queue.push_back(TreeNodeHandle(n.node->right, n.x + 1, n.y + 1));
+            }
+        }
+
+    public:
+        verticals_iter(std::deque<TreeNodeHandle> queue)
+            : queue(queue)
+        {
+            if (queue.front().node == nullptr) {
+                queue.pop_front();
+            }
+        }
+
+        bool operator!=(const verticals_iter& other) const
+        {
+            return queue != other.queue;
+        }
+
+        verticals_iter operator++()
+        {
+            advance();
+            queue.pop_front();
+            return *this;
+        }
+
+        TreeNodeHandle& operator*()
+        {
+            return queue.front();
+        }
+    };
+
+public:
+    verticals(TreeNode* root)
+        : root(root)
+    {
+    }
+
+    verticals_iter begin() const
+    {
+        return verticals_iter(std::deque { TreeNodeHandle(root, 0, 0) });
+    }
+
+    verticals_iter end() const
+    {
+        std::deque<TreeNodeHandle> q;
+        return verticals_iter(q);
+    }
+};
+
+}
+
+class Solution {
+public:
+    std::vector<std::vector<int>> verticalTraversal(TreeNode* root)
+    {
+        std::map<int, std::vector<TreeNodeHandle>> traversals;
+
+        int min_x = 0;
+        int max_x = 0;
+
+        for (auto node : verticals(root)) {
+            traversals[node.x].push_back(node);
+
+            min_x = std::min(min_x, node.x);
+            max_x = std::max(max_x, node.x);
+        }
+
+        std::vector<std::vector<int>> result;
+
+        for (int x = min_x; x <= max_x; x++) {
+            auto& v = traversals[x];
+
+            if (v.size()) {
+                std::sort(v.begin(), v.end());
+                result.push_back(std::vector<int> {});
+
+                for (auto& n : v) {
+                    result.back().push_back(n.value());
+                }
+            }
+        }
+
+        return result;
+    }
+};
+
+#pragma region tests
+
+#include <gtest/gtest.h>
+
+namespace _tests {
+
+TreeNode* construct_tree(const std::vector<int>& values, std::size_t i = 0)
+{
+    if (i >= values.size() || values[i] == -1) {
+        return nullptr;
+    }
+
+    auto tree = new TreeNode(values[i]);
+    tree->left = construct_tree(values, 2 * i + 1);
+    tree->right = construct_tree(values, 2 * i + 2);
+
+    return tree;
+}
+
+void destruct_tree(TreeNode* ptr)
+{
+    if (ptr == nullptr) {
+        return;
+    }
+
+    destruct_tree(ptr->left);
+    destruct_tree(ptr->right);
+    delete ptr;
+}
+
+}
+
+TEST(examples, first)
+{
+    Solution s;
+
+    auto t = _tests::construct_tree(std::vector { 3, 9, 20, -1, -1, 15, 7 });
+    EXPECT_EQ(s.verticalTraversal(t), (std::vector { std::vector { 9 }, std::vector { 3, 15 }, std::vector { 20 }, std::vector { 7 } }));
+    _tests::destruct_tree(t);
+}
+
+TEST(examples, second)
+{
+    Solution s;
+
+    auto t = _tests::construct_tree(std::vector { 1, 2, 3, 4, 5, 6, 7 });
+    EXPECT_EQ(s.verticalTraversal(t), (std::vector { std::vector { 4 }, std::vector { 2 }, std::vector { 1, 5, 6 }, std::vector { 3 }, std::vector { 7 } }));
+    _tests::destruct_tree(t);
+}
+
+TEST(examples, third)
+{
+    Solution s;
+
+    auto t = _tests::construct_tree(std::vector { 1, 2, 3, 4, 6, 5, 7 });
+    EXPECT_EQ(s.verticalTraversal(t), (std::vector { std::vector { 4 }, std::vector { 2 }, std::vector { 1, 5, 6 }, std::vector { 3 }, std::vector { 7 } }));
+    _tests::destruct_tree(t);
+}
+
+TEST(submission, first)
+{
+    Solution s;
+
+    auto t = _tests::construct_tree(std::vector { 3, 1, 4, 0, 2, 2 });
+    EXPECT_EQ(s.verticalTraversal(t), (std::vector { std::vector { 0 }, std::vector { 1 }, std::vector { 3, 2, 2 }, std::vector { 4 } }));
+    _tests::destruct_tree(t);
+}
+
+int main(int argc, char** argv)
+{
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}
+
+#pragma endregion /* tests */