Merge pull request #691 from fartem/96_Unique_Binary_Search_Trees

2024-07-29 v. 6.3.3: added "96. Unique Binary Search Trees"

Author: fartem

README.md

@@ -498,3 +498,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 86. Partition List                                          | [Link](https://leetcode.com/problems/partition-list/)                                          | [Link](./lib/medium/86_partition_list.rb)                                          |
 | 92. Reverse Linked List II                                  | [Link](https://leetcode.com/problems/reverse-linked-list-ii/)                                  | [Link](./lib/medium/92_reverse_linked_list_ii.rb)                                  |
 | 95. Unique Binary Search Trees II                           | [Link](https://leetcode.com/problems/unique-binary-search-trees-ii/)                           | [Link](./lib/medium/95_unique_binary_search_trees_ii.rb)                           |
+| 96. Unique Binary Search Trees                              | [Link](https://leetcode.com/problems/unique-binary-search-trees/)                              | [Link](./lib/medium/96_unique_binary_search_trees.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 = '6.3.2'
+  s.version = '6.3.3'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/96_unique_binary_search_trees.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/unique-binary-search-trees/
+# @param {Integer} n
+# @return {Integer}
+def num_trees(n)
+  arr = ::Array.new(n + 2, 0)
+  arr[0] = arr[1] = 1
+
+  (2..n).each do |i|
+    (0...i).each do |j|
+      arr[i] += arr[j] * arr[i - j - 1]
+    end
+  end
+
+  arr[n]
+end

test/medium/test_96_unique_binary_search_trees.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/96_unique_binary_search_trees'
+require 'minitest/autorun'
+
+class UniqueBinarySearchTreesTest < ::Minitest::Test
+  def test_default
+    assert_equal(5, num_trees(3))
+    assert_equal(1, num_trees(1))
+  end
+end