From 9b94b3cc54c940175187a3de41820916c141569c Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Wed, 23 Oct 2024 07:24:54 +0300
Subject: [PATCH] 2024-10-23 v. 6.8.7: added "331. Verify Preorder
 Serialization of a Binary Tree"

---
 README.md                                     |  1 +
 leetcode-ruby.gemspec                         |  2 +-
 ...preorder_serialization_of_a_binary_tree.rb | 22 +++++++++++++
 ...preorder_serialization_of_a_binary_tree.rb | 31 +++++++++++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 lib/medium/331_verify_preorder_serialization_of_a_binary_tree.rb
 create mode 100644 test/medium/test_331_verify_preorder_serialization_of_a_binary_tree.rb

diff --git a/README.md b/README.md
index aa31f29c..28355770 100644
--- a/README.md
+++ b/README.md
@@ -552,3 +552,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 316. Remove Duplicate Letters                                   | [Link](https://leetcode.com/problems/remove-duplicate-letters/)                                   | [Link](./lib/medium/316_remove_duplicate_letters.rb)                                   | [Link](./test/medium/test_316_remove_duplicate_letters.rb)                                   |
 | 318. Maximum Product of Word Lengths                            | [Link](https://leetcode.com/problems/maximum-product-of-word-lengths/)                            | [Link](./lib/medium/318_maximum_product_of_word_lengths.rb)                            | [Link](./test/medium/test_318_maximum_product_of_word_lengths.rb)                            |
 | 328. Odd Even Linked List                                       | [Link](https://leetcode.com/problems/odd-even-linked-list/)                                       | [Link](./lib/medium/328_odd_even_linked_list.rb)                                       | [Link](./test/medium/test_328_odd_even_linked_list.rb)                                       |
+| 331. Verify Preorder Serialization of a Binary Tree             | [Link](https://leetcode.com/problems/verify-preorder-serialization-of-a-binary-tree/)             | [Link](./lib/medium/331_verify_preorder_serialization_of_a_binary_tree.rb)             | [Link](./test/medium/test_331_verify_preorder_serialization_of_a_binary_tree.rb)             |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index e86b245b..772bc97e 100644
--- a/leetcode-ruby.gemspec
+++ b/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 = '6.8.6'
+  s.version = '6.8.7'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/331_verify_preorder_serialization_of_a_binary_tree.rb b/lib/medium/331_verify_preorder_serialization_of_a_binary_tree.rb
new file mode 100644
index 00000000..9e55936e
--- /dev/null
+++ b/lib/medium/331_verify_preorder_serialization_of_a_binary_tree.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/verify-preorder-serialization-of-a-binary-tree/
+# @param {String} preorder
+# @return {Boolean}
+def is_valid_serialization(preorder)
+  stack = []
+  tree = preorder.split(',')
+  tree.each do |node|
+    while node == '#' && !stack.empty? && stack.last == '#'
+      stack.pop
+
+      return false if stack.empty?
+
+      stack.pop
+    end
+
+    stack.push(node)
+  end
+
+  stack.size == 1 && stack.first == '#'
+end
diff --git a/test/medium/test_331_verify_preorder_serialization_of_a_binary_tree.rb b/test/medium/test_331_verify_preorder_serialization_of_a_binary_tree.rb
new file mode 100644
index 00000000..2f1ee420
--- /dev/null
+++ b/test/medium/test_331_verify_preorder_serialization_of_a_binary_tree.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/331_verify_preorder_serialization_of_a_binary_tree'
+require 'minitest/autorun'
+
+class VerifyPreorderSerializationOfABinaryTreeTest < ::Minitest::Test
+  def test_default_one
+    assert(
+      is_valid_serialization(
+        '9,3,4,#,#,1,#,#,2,#,6,#,#'
+      )
+    )
+  end
+
+  def test_default_two
+    assert(
+      !is_valid_serialization(
+        '1,#'
+      )
+    )
+  end
+
+  def test_default_three
+    assert(
+      !is_valid_serialization(
+        '9,#,#,1'
+      )
+    )
+  end
+end