2024-08-31 v. 6.3.6: added "102. Binary Tree Level Order Traversal"

Author: fartem

README.md

@@ -501,3 +501,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 96. Unique Binary Search Trees                              | [Link](https://leetcode.com/problems/unique-binary-search-trees/)                              | [Link](./lib/medium/96_unique_binary_search_trees.rb)                              |
 | 98. Validate Binary Search Tree                             | [Link](https://leetcode.com/problems/validate-binary-search-tree/)                             | [Link](./lib/medium/98_validate_binary_search_tree.rb)                             |
 | 99. Recover Binary Search Tree                              | [Link](https://leetcode.com/problems/recover-binary-search-tree/)                              | [Link](./lib/medium/99_recover_binary_search_tree.rb)                              |
+| 102. Binary Tree Level Order Traversal                      | [Link](https://leetcode.com/problems/binary-tree-level-order-traversal/)                       | [Link](./lib/medium/102_binary_tree_level_order_traversal.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 = '6.3.5'
+  s.version = '6.3.6'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/102_binary_tree_level_order_traversal.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+# @param {TreeNode} root
+# @return {Integer[][]}
+def level_order(root)
+  return [] unless root
+
+  result = []
+  deq = [root]
+  until deq.empty?
+    level = []
+    size = deq.size
+    (0...size).reverse_each do |_i|
+      node = deq.shift
+      level << node.val
+      deq << node.left if node.left
+      deq << node.right if node.right
+    end
+
+    result << level
+  end
+
+  result
+end

test/medium/test_102_binary_tree_level_order_traversal.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/102_binary_tree_level_order_traversal'
+require 'minitest/autorun'
+
+class BinaryTreeLevelOrderTraversalTest < ::Minitest::Test
+  def test_default
+    assert_equal(
+      [[3], [9, 20], [15, 7]],
+      level_order(
+        ::TreeNode.new(
+          3,
+          ::TreeNode.new(9),
+          ::TreeNode.new(
+            20,
+            ::TreeNode.new(15),
+            ::TreeNode.new(7)
+          )
+        )
+      )
+    )
+    assert_equal([[1]], level_order(::TreeNode.new(1)))
+    assert_equal([], level_order(nil))
+  end
+end