Merge pull request #683 from fartem/62_Unique_Paths

2024-07-22 v. 6.2.4: added "62. Unique Paths"

Author: fartem

README.md

@@ -488,4 +488,5 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 56. Merge Intervals                                         | [Link](https://leetcode.com/problems/merge-intervals/)                                         | [Link](./lib/medium/56_merge_intervals.rb)                                         |
 | 57. Insert Interval                                         | [Link](https://leetcode.com/problems/insert-interval/)                                         | [Link](./lib/medium/57_insert_interval.rb)                                         |
 | 59. Spiral Matrix II                                        | [Link](https://leetcode.com/problems/spiral-matrix-ii/)                                        | [Link](./lib/medium/59_spiral_matrix_ii.rb)                                        |
-| 61. Rotate ListII                                           | [Link](https://leetcode.com/problems/rotate-list/)                                             | [Link](./lib/medium/61_rotate_list.rb)                                             |
+| 61. Rotate List                                             | [Link](https://leetcode.com/problems/rotate-list/)                                             | [Link](./lib/medium/61_rotate_list.rb)                                             |
+| 62. Unique Paths                                            | [Link](https://leetcode.com/problems/unique-paths/)                                            | [Link](./lib/medium/62_unique_paths.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 = '6.2.3.2'
+  s.version = '6.2.4'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/62_unique_paths.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/unique-paths/
+# @param {Integer} m
+# @param {Integer} n
+# @return {Integer}
+def unique_paths(m, n)
+  find_paths({}, m, n)
+end
+
+private
+
+# @param {Hash} map
+# @param {Integer} m
+# @param {Integer} n
+# @return {Integer}
+def find_paths(map, m, n)
+  return [m, n].min if m < 2 || n < 2
+
+  cell = "#{m},#{n}"
+
+  return map[cell] if map.key?(cell)
+
+  l = find_paths(map, m, n - 1)
+  r = find_paths(map, m - 1, n)
+
+  map[cell] = l + r
+
+  l + r
+end

test/medium/test_62_unique_paths.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/62_unique_paths'
+require 'minitest/autorun'
+
+class UniquePathsTest < ::Minitest::Test
+  def test_default
+    assert_equal(28, unique_paths(3, 7))
+    assert_equal(3, unique_paths(3, 2))
+  end
+end