2025-01-22 v. 8.2.2: added "1008. Construct Binary Search Tree from Preorder Traversal"

Author: fartem

README.md

@@ -654,6 +654,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 985. Sum of Even Numbers After Queries                           | [Link](https://leetcode.com/problems/sum-of-even-numbers-after-queries/)                           | [Link](./lib/medium/985_sum_of_even_numbers_after_queries.rb)                           | [Link](./test/medium/test_985_sum_of_even_numbers_after_queries.rb)                           |
 | 988. Smallest String Starting From Leaf                          | [Link](https://leetcode.com/problems/smallest-string-starting-from-leaf/)                          | [Link](./lib/medium/988_smallest_string_starting_from_leaf.rb)                          | [Link](./test/medium/test_988_smallest_string_starting_from_leaf.rb)                          |
 | 998. Maximum Binary Tree II                                      | [Link](https://leetcode.com/problems/maximum-binary-tree-ii/)                                      | [Link](./lib/medium/998_maximum_binary_tree_ii.rb)                                      | [Link](./test/medium/test_998_maximum_binary_tree_ii.rb)                                      |
+| 1008. Construct Binary Search Tree from Preorder Traversal       | [Link](https://leetcode.com/problems/construct-binary-search-tree-from-preorder-traversal/)        | [Link](./lib/medium/1008_construct_binary_search_tree_from_preorder_traversal.rb)       | [Link](./test/medium/test_1008_construct_binary_search_tree_from_preorder_traversal.rb)       |
 | 1400. Construct K Palindrome Strings                             | [Link](https://leetcode.com/problems/construct-k-palindrome-strings/)                              | [Link](./lib/medium/1400_construct_k_palindrome_strings.rb)                             | [Link](./test/medium/test_1400_construct_k_palindrome_strings.rb)                             |
 | 2116. Check if a Parentheses String Can Be Valid                 | [Link](https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid/)                  | [Link](./lib/medium/2116_check_if_a_parentheses_string_can_be_valid.rb)                 | [Link](./test/medium/test_2116_check_if_a_parentheses_string_can_be_valid.rb)                 |
 | 2425. Bitwise XOR of All Pairings                                | [Link](https://leetcode.com/problems/bitwise-xor-of-all-pairings/)                                 | [Link](./lib/medium/2425_bitwise_xor_of_all_pairings.rb)                                | [Link](./test/medium/test_2425_bitwise_xor_of_all_pairings.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 = '8.2.1'
+  s.version = '8.2.2'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/1008_construct_binary_search_tree_from_preorder_traversal.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative '../common/binary_tree'
+
+# https://leetcode.com/problems/construct-binary-search-tree-from-preorder-traversal/
+# @param {Integer[]} preorder
+# @return {TreeNode}
+def bst_from_preorder(preorder)
+  construct_bst_from_preorder(preorder, 0, preorder.size - 1)
+end
+
+private
+
+# @param {Integer[]} preorder
+# @param {Integer} start
+# @param {Integer} nd
+# @return {TreeNode}
+def construct_bst_from_preorder(preorder, start, nd)
+  return if start > nd
+
+  node = ::TreeNode.new(preorder[start])
+
+  index = start
+  while index <= nd
+    break if preorder[index] > node.val
+
+    index += 1
+  end
+
+  node.left = construct_bst_from_preorder(preorder, start + 1, index - 1)
+  node.right = construct_bst_from_preorder(preorder, index, nd)
+
+  node
+end

lib/medium/988_smallest_string_starting_from_leaf.rb

@@ -13,7 +13,7 @@ def smallest_from_leaf(root)
 private
 
 # @param {TreeNode} root
-# @param {Array} curr
+# @param {String} curr
 # @return {Void}
 def find_smallest_string_staring_from_leaf(root, curr)
   return unless root

test/medium/test_1008_construct_binary_search_tree_from_preorder_traversal.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/1008_construct_binary_search_tree_from_preorder_traversal'
+require 'minitest/autorun'
+
+class ConstructBinarySearchTreeFromPreorderTraversalTest < ::Minitest::Test
+  def test_default_one
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          8,
+          ::TreeNode.new(
+            5,
+            ::TreeNode.new(1),
+            ::TreeNode.new(7)
+          ),
+          ::TreeNode.new(
+            10,
+            nil,
+            ::TreeNode.new(12)
+          )
+        ),
+        bst_from_preorder(
+          [8, 5, 1, 7, 10, 12]
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          1,
+          nil,
+          ::TreeNode.new(3)
+        ),
+        bst_from_preorder(
+          [1, 3]
+        )
+      )
+    )
+  end
+end