Merge pull request #799 from fartem/560-Subarray-Sum-Equals-K

2024-12-10 v. 7.2.8: added "560. Subarray Sum Equals K"

Author: fartem

README.md

@@ -593,3 +593,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 535. Encode and Decode TinyURL                                  | [Link](https://leetcode.com/problems/encode-and-decode-tinyurl/)                                  | [Link](./lib/medium/535_encode_and_decode_tinyurl.rb)                                  | [Link](./test/medium/test_535_encode_and_decode_tinyurl.rb)                                  |
 | 538. Convert BST to Greater Tree                                | [Link](https://leetcode.com/problems/convert-bst-to-greater-tree/)                                | [Link](./lib/medium/538_convert_bst_to_greater_tree.rb)                                | [Link](./test/medium/test_538_convert_bst_to_greater_tree.rb)                                |
 | 556. Next Greater Element III                                   | [Link](https://leetcode.com/problems/next-greater-element-iii/)                                   | [Link](./lib/medium/556_next_greater_element_iii.rb)                                   | [Link](./test/medium/test_556_next_greater_element_iii.rb)                                   |
+| 560. Subarray Sum Equals K                                      | [Link](https://leetcode.com/problems/subarray-sum-equals-k/)                                      | [Link](./lib/medium/560_subarray_sum_equals_k.rb)                                      | [Link](./test/medium/test_560_subarray_sum_equals_k.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 = '7.2.7'
+  s.version = '7.2.8'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/560_subarray_sum_equals_k.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/subarray-sum-equals-k/
+# @param {Integer[]} nums
+# @param {Integer} k
+# @return {Integer}
+def subarray_sum(nums, k)
+  result = 0
+  pre = 0
+  values = {}
+  values[0] = 1
+
+  nums.each do |num|
+    pre += num
+    result += values.fetch(pre - k, 0)
+    values[pre] = values.fetch(pre, 0) + 1
+  end
+
+  result
+end

test/medium/test_560_subarray_sum_equals_k.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/560_subarray_sum_equals_k'
+require 'minitest/autorun'
+
+class SubarraySumEqualsKTest < ::Minitest::Test
+  def test_default_one = assert_equal(2, subarray_sum([1, 1, 1], 2))
+
+  def test_default_two = assert_equal(2, subarray_sum([1, 2, 3], 3))
+end