2025-03-04 v. 8.8.0: added "1721. Swapping Nodes in a Linked List"

Author: fartem

README.md

@@ -713,6 +713,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 1679. Max Number of K-Sum Pairs                                                     | [Link](https://leetcode.com/problems/max-number-of-k-sum-pairs/)                                                     | [Link](./lib/medium/1679_max_number_of_k_sum_pairs.rb)                                                     | [Link](./test/medium/test_1679_max_number_of_k_sum_pairs.rb)                                                     |
 | 1685. Sum of Absolute Differences in a Sorted Array                                 | [Link](https://leetcode.com/problems/sum-of-absolute-differences-in-a-sorted-array/)                                 | [Link](./lib/medium/1685_sum_of_absolute_differences_in_a_sorted_array.rb)                                 | [Link](./test/medium/test_1685_sum_of_absolute_differences_in_a_sorted_array.rb)                                 |
 | 1706. Where Will the Ball Fall                                                      | [Link](https://leetcode.com/problems/where-will-the-ball-fall/)                                                      | [Link](./lib/medium/1706_where_will_the_ball_fall.rb)                                                      | [Link](./test/medium/test_1706_where_will_the_ball_fall.rb)                                                      |
+| 1721. Swapping Nodes in a Linked List                                               | [Link](https://leetcode.com/problems/swapping-nodes-in-a-linked-list/)                                               | [Link](./lib/medium/1721_swapping_nodes_in_a_linked_list.rb)                                               | [Link](./test/medium/test_1721_swapping_nodes_in_a_linked_list.rb)                                               |
 | 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)                                    |
 | 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)                                                                  |

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 = '8.7.9'
+  s.version = '8.8.0'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/common/linked_list.rb

@@ -11,7 +11,7 @@ def initialize(val = 0, nxt = nil)
     @next = nxt
   end
 
-  # @param {Array} values
+  # @param {ListNode} values
   def self.from_array(values)
     return if values.empty?
 

lib/medium/1721_swapping_nodes_in_a_linked_list.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/swapping-nodes-in-a-linked-list/
+# @param {ListNode} head
+# @param {Integer} k
+# @return {ListNode}
+def swap_nodes(head, k)
+  nodes = []
+  pointer = head
+
+  while pointer
+    nodes << pointer
+
+    pointer = pointer.next
+  end
+
+  first = nodes[k - 1]
+  second = nodes[nodes.size - k]
+  temp = first.val
+  first.val = second.val
+  second.val = temp
+
+  head
+end

test/medium/test_1721_swapping_nodes_in_a_linked_list.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/linked_list'
+require_relative '../../lib/medium/1721_swapping_nodes_in_a_linked_list'
+require 'minitest/autorun'
+
+class SwappingNodesInALindedListTest < ::Minitest::Test
+  def test_default_one
+    assert(
+      ::ListNode.are_equals(
+        ::ListNode.from_array(
+          [1, 4, 3, 2, 5]
+        ),
+        swap_nodes(
+          ::ListNode.from_array(
+            [1, 2, 3, 4, 5]
+          ),
+          2
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert(
+      ::ListNode.are_equals(
+        ::ListNode.from_array(
+          [7, 9, 6, 6, 8, 7, 3, 0, 9, 5]
+        ),
+        swap_nodes(
+          ::ListNode.from_array(
+            [7, 9, 6, 6, 7, 8, 3, 0, 9, 5]
+          ),
+          5
+        )
+      )
+    )
+  end
+end