2025-01-27 v. 8.2.9: added "1081. Smallest Subsequence of Distinct Characters"

Author: fartem

README.md

@@ -661,6 +661,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 1038. Binary Search Tree to Greater Sum Tree                     | [Link](https://leetcode.com/problems/binary-search-tree-to-greater-sum-tree/)                      | [Link](./lib/medium/1038_binary_search_tree_to_greater_sum_tree.rb)                     | [Link](./test/medium/test_1038_binary_search_tree_to_greater_sum_tree.rb)                     |
 | 1043. Partition Array for Maximum Sum                            | [Link](https://leetcode.com/problems/partition-array-for-maximum-sum/)                             | [Link](./lib/medium/1043_partition_array_for_maximum_sum.rb)                            | [Link](./test/medium/test_1043_partition_array_for_maximum_sum.rb)                            |
 | 1079. Letter Tile Possibilities                                  | [Link](https://leetcode.com/problems/letter-tile-possibilities/)                                   | [Link](./lib/medium/1079_letter_tile_possibilities.rb)                                  | [Link](./test/medium/test_1079_letter_tile_possibilities.rb)                                  |
+| 1081. Smallest Subsequence of Distinct Characters                | [Link](https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/)                 | [Link](./lib/medium/1081_smallest_subsequence_of_distinct_characters.rb)                | [Link](./test/medium/test_1081_smallest_subsequence_of_distinct_characters.rb)                |
 | 1400. Construct K Palindrome Strings                             | [Link](https://leetcode.com/problems/construct-k-palindrome-strings/)                              | [Link](./lib/medium/1400_construct_k_palindrome_strings.rb)                             | [Link](./test/medium/test_1400_construct_k_palindrome_strings.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)                                |

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 = '8.2.8'
+  s.version = '8.2.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/1081_smallest_subsequence_of_distinct_characters.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/
+# @param {String} s
+# @return {String}
+def smallest_subsequence(s)
+  last_indices = {}
+  s.each_char.with_index { |c, i| last_indices[c] = i }
+
+  seen = ::Set.new
+  stack = []
+
+  s.each_char.with_index do |c, i|
+    next if seen.include?(c)
+
+    seen.delete(stack.pop) while !stack.empty? && c < stack.last && i < last_indices[stack.last]
+
+    stack << c
+    seen << c
+  end
+
+  stack.join
+end

test/medium/test_1081_smallest_subsequence_of_distinct_characters.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/1081_smallest_subsequence_of_distinct_characters'
+require 'minitest/autorun'
+
+class SmallestSubsequenceOfDistinctCharactersTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      'abc',
+      smallest_subsequence('bcabc')
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      'acdb',
+      smallest_subsequence('cbacdcbc')
+    )
+  end
+end