2024-10-30 v. 6.9.2: added "377. Combination Sum IV"

Author: fartem

README.md

@@ -557,3 +557,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 341. Flatten Nested List Iterator                               | [Link](https://leetcode.com/problems/flatten-nested-list-iterator/)                               | [Link](./lib/medium/341_flatten_nested_list_iterator.rb)                               | [Link](./test/medium/test_341_flatten_nested_list_iterator.rb)                               |
 | 347. Top K Frequent Elements                                    | [Link](https://leetcode.com/problems/top-k-frequent-elements/)                                    | [Link](./lib/medium/347_top_k_frequent_elements.rb)                                    | [Link](./test/medium/test_347_top_k_frequent_elements.rb)                                    |
 | 371. Sum of Two Integers                                        | [Link](https://leetcode.com/problems/sum-of-two-integers/)                                        | [Link](./lib/medium/371_sum_of_two_integers.rb)                                        | [Link](./test/medium/test_371_sum_of_two_integers.rb)                                        |
+| 377. Combination Sum IV                                         | [Link](https://leetcode.com/problems/combination-sum-iv/)                                         | [Link](./lib/medium/377_combination_sum_iv.rb)                                         | [Link](./test/medium/test_377_combination_sum_iv.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 = '6.9.1'
+  s.version = '6.9.2'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/377_combination_sum_iv.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/combination-sum-iv/
+# @param {Integer[]} nums
+# @param {Integer} target
+# @return {Integer}
+def combination_sum4(nums, target)
+  find(nums, ::Array.new(target + 1, -1), target)
+end
+
+private
+
+# @param {Integer[]} nums
+# @param {Integer[]} memo
+# @param {Integer} target
+# @return {Integer}
+def find(nums, memo, target)
+  return 1 if target.zero?
+
+  return 0 if target.negative?
+
+  if memo[target] == -1
+    memo[target] = 0
+    nums.each { |num| memo[target] += find(nums, memo, target - num) }
+  end
+
+  memo[target]
+end

test/medium/test_377_combination_sum_iv.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/377_combination_sum_iv'
+require 'minitest/autorun'
+
+class CombinationSumIVTest < ::Minitest::Test
+  def test_default_one = assert_equal(7, combination_sum4([1, 2, 3], 4))
+
+  def test_default_two = assert_equal(0, combination_sum4([9], 3))
+end