2024-07-15 v. 6.1.4: added "46. Permutations"

Author: fartem

README.md

@@ -479,3 +479,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 38. Count and Say                                           | [Link](https://leetcode.com/problems/count-and-say/)                                           | [Link](./lib/medium/38_count_and_say.rb)                                           |
 | 39. Combination Sum                                         | [Link](https://leetcode.com/problems/combination-sum/)                                         | [Link](./lib/medium/39_combination_sum.rb)                                         |
 | 43. Multiply Strings                                        | [Link](https://leetcode.com/problems/multiply-strings/)                                        | [Link](./lib/medium/43_multiply_strings.rb)                                        |
+| 46. Permutations                                            | [Link](https://leetcode.com/problems/permutations/)                                            | [Link](./lib/medium/46_permutations.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 = '6.1.3'
+  s.version = '6.1.4'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[bin/leetcode-ruby README.md LICENSE]
   s.executable = 'leetcode-ruby'

lib/medium/46_permutations.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/permutations/
+# @param {Integer[]} nums
+# @return {Integer[][]}
+def permute(nums)
+  result = []
+  permutations(nums, [], result, [])
+
+  result
+end
+
+private
+
+# @param {Integer[]} nums
+# @param {Integer[]} d_s
+# @param {Integer[]} result
+# @param {Boolean[]} freq
+def permutations(nums, d_s, result, freq)
+  if d_s.length == nums.length
+    result << d_s.clone
+  else
+    (0...nums.length).each do |i|
+      next if freq[i]
+
+      freq[i] = true
+      d_s << nums[i]
+      permutations(nums, d_s, result, freq)
+      d_s.delete_at(d_s.length - 1)
+      freq[i] = false
+    end
+  end
+end

test/medium/test_46_permutations.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/46_permutations'
+require 'minitest/autorun'
+
+class PermutationsTest < ::Minitest::Test
+  def test_default
+    assert_equal(
+      [
+        [1, 2, 3],
+        [1, 3, 2],
+        [2, 1, 3],
+        [2, 3, 1],
+        [3, 1, 2],
+        [3, 2, 1]
+      ],
+      permute([1, 2, 3])
+    )
+    assert_equal([[0, 1], [1, 0]], permute([0, 1]))
+    assert_equal([[1]], permute([1]))
+  end
+end