2024-11-11 v. 7.0.0: added "402. Remove K Digits"

Author: fartem

README.md

@@ -565,3 +565,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 394. Decode String                                              | [Link](https://leetcode.com/problems/decode-string/)                                              | [Link](./lib/medium/394_decode_string.rb)                                              | [Link](./test/medium/test_394_decode_string.rb)                                              |
 | 398. Random Pick Index                                          | [Link](https://leetcode.com/problems/random-pick-index/)                                          | [Link](./lib/medium/398_random_pick_index.rb)                                          | [Link](./test/medium/test_398_random_pick_index.rb)                                          |
 | 400. Nth Digit                                                  | [Link](https://leetcode.com/problems/nth-digit/)                                                  | [Link](./lib/medium/400_nth_digit.rb)                                                  | [Link](./test/medium/test_400_nth_digit.rb)                                                  |
+| 402. Remove K Digits                                            | [Link](https://leetcode.com/problems/remove-k-digits/)                                            | [Link](./lib/medium/402_remove_k_digits.rb)                                            | [Link](./test/medium/test_402_remove_k_digits.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 = '6.9.9'
+  s.version = '7.0.0'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/402_remove_k_digits.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/remove-k-digits/
+# @param {String} num
+# @param {Integer} k
+# @return {String}
+def remove_kdigits(num, k)
+  return '0' if num.size == k
+
+  stack = []
+  i = 0
+  while i < num.size
+    while k.positive? && !stack.empty? && stack.last > num[i]
+      stack.pop
+      k -= 1
+    end
+
+    stack << num[i]
+    i += 1
+  end
+
+  while k.positive?
+    stack.pop
+    k -= 1
+  end
+
+  result = []
+  result << stack.pop until stack.empty?
+
+  result.reverse!
+  result.delete_at(0) while result.size > 1 && result[0] == '0'
+
+  result.join
+end

test/medium/test_402_remove_k_digits.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/402_remove_k_digits'
+require 'minitest/autorun'
+
+class RemoveKDigitsTest < ::Minitest::Test
+  def test_default_one = assert_equal('1219', remove_kdigits('1432219', 3))
+
+  def test_default_two = assert_equal('200', remove_kdigits('10200', 1))
+
+  def test_default_three = assert_equal('0', remove_kdigits('10', 2))
+
+  def test_additional_one = assert_equal('11', remove_kdigits('112', 1))
+end