2025-03-19 v. 9.0.3: added "2130. Maximum Twin Sum of a Linked List"

Author: fartem

README.md

@@ -737,6 +737,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 2116. Check if a Parentheses String Can Be Valid                                    | [Link](https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid/)                                    | [Link](./lib/medium/2116_check_if_a_parentheses_string_can_be_valid.rb)                                    | [Link](./test/medium/test_2116_check_if_a_parentheses_string_can_be_valid.rb)                                    |
 | 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)                                             |
 | 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)                                    |

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 = '9.0.2'
+  s.version = '9.0.3'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/2130_maximum_twin_sum_of_a_linked_list.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/maximum-twin-sum-of-a-linked-list/
+# @param {ListNode} head
+# @return {Integer}
+def pair_sum(head)
+  slow = head
+  fast = head
+  first_part = head
+
+  while fast&.next
+    first_part = slow
+    slow = slow.next
+    fast = fast.next.next
+  end
+
+  prev = nil
+
+  while slow
+    nxt = slow.next
+    slow.next = prev
+    prev = slow
+    slow = nxt
+  end
+
+  first_part.next = prev
+  result = 0
+  f = head
+  s = first_part.next
+
+  while s
+    result = [result, f.val + s.val].max
+    f = f.next
+    s = s.next
+  end
+
+  result
+end

test/medium/test_2130_maximum_twin_sum_of_a_linked_list.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/linked_list'
+require_relative '../../lib/medium/2130_maximum_twin_sum_of_a_linked_list'
+require 'minitest/autorun'
+
+class MaximumTwinSumOfALinkedListTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      6,
+      pair_sum(
+        ::ListNode.from_array(
+          [5, 4, 2, 1]
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      7,
+      pair_sum(
+        ::ListNode.from_array(
+          [4, 2, 2, 3]
+        )
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      100_001,
+      pair_sum(
+        ::ListNode.from_array(
+          [1, 100_000]
+        )
+      )
+    )
+  end
+end