2025-01-27 v. 8.2.8: added "1079. Letter Tile Possibilities"

Author: fartem

README.md

@@ -660,6 +660,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 1026. Maximum Difference Between Node and Ancestor               | [Link](https://leetcode.com/problems/maximum-difference-between-node-and-ancestor/)                | [Link](./lib/medium/1026_maximum_difference_between_node_and_ancestor.rb)               | [Link](./test/medium/test_1026_maximum_difference_between_node_and_ancestor.rb)               |
 | 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)                                  |
 | 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 = '8.2.7'
+  s.version = '8.2.8'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/1079_letter_tile_possibilities.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/letter-tile-possibilities/
+# @param {String} tiles
+# @return {Integer}
+def num_tile_possibilities(tiles)
+  @count = 0
+
+  chars = tiles.chars.sort
+  backtrack(chars, ::Array.new(chars.size, false))
+
+  @count - 1
+end
+
+private
+
+# @param {String[]} chars
+# @param {Boolean[]} used
+# @return {Void}
+def backtrack(chars, used)
+  @count += 1
+
+  chars.each_with_index do |char, i|
+    next if used[i] || (i.positive? && char == chars[i - 1] && !used[i - 1])
+
+    used[i] = true
+    backtrack(chars, used)
+    used[i] = false
+  end
+end

test/medium/test_1079_letter_tile_possibilities.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/1079_letter_tile_possibilities'
+require 'minitest/autorun'
+
+class LetterTilePossibilitiesTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      8,
+      num_tile_possibilities(
+        'AAB'
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      188,
+      num_tile_possibilities(
+        'AAABBC'
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      1,
+      num_tile_possibilities(
+        'V'
+      )
+    )
+  end
+end