2025-01-03 v. 7.6.9: added "32. Longest Valid Parentheses"

README.md

@@ -638,3 +638,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 23. Merge k Sorted Lists                      | [Link](https://leetcode.com/problems/merge-k-sorted-lists/)                      | [Link](./lib/hard/23_merge_k_sorted_lists.rb)                      | [Link](./test/hard/test_23_merge_k_sorted_lists.rb)                      |
 | 25. Reverse Nodes in k-Group                  | [Link](https://leetcode.com/problems/reverse-nodes-in-k-group/)                  | [Link](./lib/hard/25_reverse_nodes_in_k_group.rb)                  | [Link](./test/hard/test_25_reverse_nodes_in_k_group.rb)                  |
 | 30. Substring with Concatenation of All Words | [Link](https://leetcode.com/problems/substring-with-concatenation-of-all-words/) | [Link](./lib/hard/30_substring_with_concatenation_of_all_words.rb) | [Link](./test/hard/test_30_substring_with_concatenation_of_all_words.rb) |
+| 32. Longest Valid Parentheses                 | [Link](https://leetcode.com/problems/longest-valid-parentheses/)                 | [Link](./lib/hard/32_longest_valid_parentheses.rb)                 | [Link](./test/hard/test_32_longest_valid_parentheses.rb)                 |

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '7.6.8.1'
+  s.version = '7.6.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/hard/32_longest_valid_parentheses.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/longest-valid-parentheses/
+# @param {String} s
+# @return {Integer}
+def longest_valid_parentheses(s)
+  stack = [-1]
+  result = 0
+  (0...s.size).each do |i|
+    if s[i] == '('
+      stack << i
+    else
+      stack.delete_at(stack.size - 1)
+
+      if stack.empty?
+        stack << i
+      else
+        result = [result, i - stack.last].max
+      end
+    end
+  end
+
+  result
+end

test/hard/test_32_longest_valid_parentheses.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/hard/32_longest_valid_parentheses'
+require 'minitest/autorun'
+
+class LongestValidParenthesesTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      2,
+      longest_valid_parentheses(
+        '(()'
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      4,
+      longest_valid_parentheses(
+        ')()())'
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      0,
+      longest_valid_parentheses(
+        ''
+      )
+    )
+  end
+end