Merge pull request #742 from fartem/236_Lowest_Common_Ancestor_of_a_Binary_Tree

2024-10-04 v. 6.7.5: added "236. Lowest Common Ancestor of a Binary Tree"

Author: fartem

README.md

@@ -540,3 +540,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 227. Basic Calculator II                                        | [Link](https://leetcode.com/problems/basic-calculator-ii/)                                        | [Link](./lib/medium/227_basic_calculator_ii.rb)                                        | [Link](./test/medium/test_227_basic_calculator_ii.rb)                                        |
 | 230. Kth Smallest Element in a BST                              | [Link](https://leetcode.com/problems/kth-smallest-element-in-a-bst/)                              | [Link](./lib/medium/230_kth_smallest_element_in_a_bst.rb)                              | [Link](./test/medium/test_230_kth_smallest_element_in_a_bst.rb)                              |
 | 235. Lowest Common Ancestor of a Binary Search Tree             | [Link](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)             | [Link](./lib/medium/235_lowest_common_ancestor_of_a_binary_search_tree.rb)             | [Link](./test/medium/test_235_lowest_common_ancestor_of_a_binary_search_tree.rb)             |
+| 236. Lowest Common Ancestor of a Binary Tree                    | [Link](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/)                    | [Link](./lib/medium/236_lowest_common_ancestor_of_a_binary_tree.rb)                    | [Link](./test/medium/test_236_lowest_common_ancestor_of_a_binary_tree.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 = '6.7.4'
+  s.version = '6.7.5'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/common/binary_tree.rb

@@ -25,4 +25,12 @@ def self.are_equals(curr, other)
     right_eq = are_equals(curr.right, other.right)
     curr_eq && left_eq && right_eq
   end
+
+  # @param {TreeNode} other
+  # @return {Boolean}
+  def ==(other)
+    return false unless other
+
+    val == other.val
+  end
 end

lib/medium/236_lowest_common_ancestor_of_a_binary_tree.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/
+# @param {TreeNode} root
+# @param {TreeNode} p
+# @param {TreeNode} q
+# @return {TreeNode}
+def lowest_common_ancestor236(root, p, q)
+  return root if [nil, p, q].index(root)
+
+  left = lowest_common_ancestor236(root.left, p, q)
+  right = lowest_common_ancestor236(root.right, p, q)
+
+  left && right ? root : left || right
+end

test/medium/test_236_lowest_common_ancestor_of_a_binary_tree.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/236_lowest_common_ancestor_of_a_binary_tree'
+require 'minitest/autorun'
+
+class LowestCommonAncestorOfABinaryTreeTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      3,
+      lowest_common_ancestor236(
+        ::TreeNode.new(
+          3,
+          ::TreeNode.new(
+            5,
+            ::TreeNode.new(6),
+            ::TreeNode.new(
+              2,
+              ::TreeNode.new(7),
+              ::TreeNode.new(4)
+            )
+          ),
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(0),
+            ::TreeNode.new(8)
+          )
+        ),
+        ::TreeNode.new(5),
+        ::TreeNode.new(1)
+      ).val
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      5,
+      lowest_common_ancestor236(
+        ::TreeNode.new(
+          3,
+          ::TreeNode.new(
+            5,
+            ::TreeNode.new(6),
+            ::TreeNode.new(
+              2,
+              ::TreeNode.new(7),
+              ::TreeNode.new(4)
+            )
+          ),
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(0),
+            ::TreeNode.new(8)
+          )
+        ),
+        ::TreeNode.new(5),
+        ::TreeNode.new(4)
+      ).val
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      1,
+      lowest_common_ancestor236(
+        ::TreeNode.new(
+          1,
+          ::TreeNode.new(2),
+          nil
+        ),
+        ::TreeNode.new(1),
+        ::TreeNode.new(2)
+      ).val
+    )
+  end
+end