Commit be89d17

@@ -0,0 +1,36 @@
+require 'bundler/inline'
+
+gemfile do
+  source 'https://rubygems.org'
+
+  gem 'minitest'
+end
+
+require 'minitest/autorun'
+
+=begin
+A Dyck word is a sequence of +1’s and -1’s with the property that the sum of any prefix
+of the sequence is never negative.
+For example, +1,−1,+1,−1 is a Dyck word, but +1,−1,−1,+1 is not a Dyck word since the prefix +1 − 1 − 1 < 0.
+
+Describe any relationship between Dyck words and Stack push(x) and pop() operations.
+=end
+
+class Example < Minitest::Test
+  def dyck_word?(stack)
+    sum = 0
+    stack.each do |item|
+      return if sum.negative?
+      sum += item
+    end
+    true
+  end
+
+  def test_valid_word
+    assert dyck_word?([1, -1, 1, -1])
+  end
+
+  def test_invalid_word
+    refute dyck_word?([1, -1, -1, 1])
+  end
+end