problems: add daily problems

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/linked-list-cycle-ii.rb

@@ -0,0 +1,27 @@
+# Definition for singly-linked list.
+# class ListNode
+#     attr_accessor :val, :next
+#     def initialize(val)
+#         @val = val
+#         @next = nil
+#     end
+# end
+
+# @param {ListNode} head
+# @return {ListNode}
+
+require 'set'
+
+def detectCycle(head)
+    def detectCycleRec(node, seen)
+        if node == nil then
+            return node
+        elsif seen.add?(node) == nil then
+            return node
+        end
+
+        return detectCycleRec(node.next, seen)
+    end
+
+    detectCycleRec(head, Set.new)
+end

problems/word-pattern.rb

@@ -0,0 +1,49 @@
+# @param {String} pattern
+# @param {String} s
+# @return {Boolean}
+def word_pattern(pattern, s)
+    words = s.split
+
+    expected_words = Hash.new
+    expected_patterns = Hash.new
+
+    pattern.chars.zip(words).each { |pat, word|
+        expected_word = expected_words[pat]
+        expected_pattern = expected_patterns[word]
+
+        if expected_pattern == nil && expected_word == nil then
+            expected_patterns[word] = pat
+            expected_words[pat] = word
+        elsif word != expected_word || pat != expected_pattern then
+            return false
+        end
+    }
+
+    return pattern.size == words.size
+end
+
+RSpec.describe "word_pattern" do
+    it "finds pattern" do
+        expect(word_pattern("abba", "dog cat cat dog")).to be true
+    end
+
+    it "finds one odd word" do
+        expect(word_pattern("abba", "dog cat cat fish")).to be false
+    end
+
+    it "finds that are not the same words" do
+        expect(word_pattern("aaaa", "dog cat cat dog")).to be false
+    end
+
+    it "handles bijection correctly" do
+        expect(word_pattern("abba", "dog dog dog dog")).to be false
+    end
+
+    it "handles correctly different length of input" do
+        expect(word_pattern("aaa", "aa aa aa aa")).to be false
+    end
+
+    it "handles correctly different length of pattern" do
+        expect(word_pattern("aaaaa", "aa aa aa aa")).to be false
+    end
+end