From 038a95f5a642561b1ef782f1a20bb3311c06cff6 Mon Sep 17 00:00:00 2001 From: fartem Date: Thu, 20 Mar 2025 06:07:09 +0300 Subject: [PATCH] 2025-03-20 v. 9.0.4: added "2131. Longest Palindrome by Concatenating Two Letter Words" --- README.md | 1 + leetcode-ruby.gemspec | 2 +- ...drome_by_concatenating_two_letter_words.rb | 43 +++++++++++++++++++ ...drome_by_concatenating_two_letter_words.rb | 34 +++++++++++++++ 4 files changed, 79 insertions(+), 1 deletion(-) create mode 100644 lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words.rb create mode 100644 test/medium/test_2131_longest_palindrome_by_concatenating_two_letter_words.rb diff --git a/README.md b/README.md index 5ad30028..801c3d0d 100644 --- a/README.md +++ b/README.md @@ -738,6 +738,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/). | 2121. Intervals Between Identical Elements | [Link](https://leetcode.com/problems/intervals-between-identical-elements/) | [Link](./lib/medium/2121_intervals_between_identical_elements.rb) | [Link](./test/medium/test_2121_intervals_between_identical_elements.rb) | | 2125. Number of Laser Beams in a Bank | [Link](https://leetcode.com/problems/number-of-laser-beams-in-a-bank/) | [Link](./lib/medium/2125_number_of_laser_beams_in_a_bank.rb) | [Link](./test/medium/test_2125_number_of_laser_beams_in_a_bank.rb) | | 2130. Maximum Twin Sum of a Linked List | [Link](https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/) | [Link](./lib/medium/2130_maximum_twin_sum_of_a_linked_list.rb) | [Link](./test/medium/test_2130_maximum_twin_sum_of_a_linked_list.rb) | +| 2131. Longest Palindrome by Concatenating Two Letter Words | [Link](https://leetcode.com/problems/longest-palindrome-by-concatenating-two-letter-words/) | [Link](./lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words.rb) | [Link](./test/medium/test_2131_longest_palindrome_by_concatenating_two_letter_words.rb) | | 2425. Bitwise XOR of All Pairings | [Link](https://leetcode.com/problems/bitwise-xor-of-all-pairings/) | [Link](./lib/medium/2425_bitwise_xor_of_all_pairings.rb) | [Link](./test/medium/test_2425_bitwise_xor_of_all_pairings.rb) | | 2429. Minimize XOR | [Link](https://leetcode.com/problems/minimize-xor/) | [Link](./lib/medium/2429_minimize_xor.rb) | [Link](./test/medium/test_2429_minimize_xor.rb) | | 2657. Find the Prefix Common Array of Two Arrays | [Link](https://leetcode.com/problems/find-the-prefix-common-array-of-two-arrays/) | [Link](./lib/medium/2657_find_the_prefix_common_array_of_two_arrays.rb) | [Link](./test/medium/test_2657_find_the_prefix_common_array_of_two_arrays.rb) | diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec index 3a371cd1..e38bc7fe 100644 --- a/leetcode-ruby.gemspec +++ b/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 = '9.0.3' + s.version = '9.0.4' s.license = 'MIT' s.files = ::Dir['lib/**/*.rb'] + %w[README.md] s.executable = 'leetcode-ruby' diff --git a/lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words.rb b/lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words.rb new file mode 100644 index 00000000..36ea1199 --- /dev/null +++ b/lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words.rb @@ -0,0 +1,43 @@ +# frozen_string_literal: true + +# https://leetcode.com/problems/longest-palindrome-by-concatenating-two-letter-words/ +# @param {String[]} words +# @return {Integer} +def longest_palindrome2131(words) + freq = ::Hash.new(0) + words.each { |word| freq[word] += 1 } + + total = 0 + processed = ::Set.new + + freq.each_key do |word| + rev = word.reverse + + next if word == rev + + next if processed.include?(word) + + processed.add(word) + processed.add(rev) + + current_count = freq[word] + rev_count = freq[rev] + min_pairs = [current_count, rev_count].min + total += min_pairs * 4 + end + + has_odd_count = false + + freq.each do |word, count| + next unless word == word.reverse + + pairs = count / 2 + total += pairs * 4 + + has_odd_count ||= count.odd? + end + + total += 2 if has_odd_count + + total +end diff --git a/test/medium/test_2131_longest_palindrome_by_concatenating_two_letter_words.rb b/test/medium/test_2131_longest_palindrome_by_concatenating_two_letter_words.rb new file mode 100644 index 00000000..c30b3e0d --- /dev/null +++ b/test/medium/test_2131_longest_palindrome_by_concatenating_two_letter_words.rb @@ -0,0 +1,34 @@ +# frozen_string_literal: true + +require_relative '../test_helper' +require_relative '../../lib/medium/2131_longest_palindrome_by_concatenating_two_letter_words' +require 'minitest/autorun' + +class LongestPalindromeByConcatenatingTwoLetterWordsTest < ::Minitest::Test + def test_default_one + assert_equal( + 6, + longest_palindrome2131( + %w[lc cl gg] + ) + ) + end + + def test_default_two + assert_equal( + 8, + longest_palindrome2131( + %w[ab ty yt lc cl ab] + ) + ) + end + + def test_default_three + assert_equal( + 2, + longest_palindrome2131( + %w[cc ll xx] + ) + ) + end +end