From bed197df3f027e5595aa6591b89c65aec7af4f57 Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Wed, 7 Aug 2024 08:48:50 +0300
Subject: [PATCH] 2024-08-76 v. 6.4.1: added "109. Convert Sorted List to
 Binary Search Tree"

---
 README.md                                     |  1 +
 leetcode-ruby.gemspec                         |  2 +-
 ...nvert_sorted_list_to_binary_search_tree.rb | 55 +++++++++++++++++++
 ...nvert_sorted_list_to_binary_search_tree.rb | 40 ++++++++++++++
 4 files changed, 97 insertions(+), 1 deletion(-)
 create mode 100644 lib/medium/109_convert_sorted_list_to_binary_search_tree.rb
 create mode 100644 test/medium/test_109_convert_sorted_list_to_binary_search_tree.rb

diff --git a/README.md b/README.md
index 07141b3e..54a63f71 100644
--- a/README.md
+++ b/README.md
@@ -506,3 +506,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 105. Construct Binary Tree from Preorder and Inorder Traversal  | [Link](https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)  | [Link](./lib/medium/105_construct_binary_tree_from_preorder_and_inorder_traversal.rb)  |
 | 106. Construct Binary Tree from Inorder and Postorder Traversal | [Link](https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/) | [Link](./lib/medium/106_construct_binary_tree_from_inorder_and_postorder_traversal.rb) |
 | 107. Binary Tree Level Order Traversal II                       | [Link](https://leetcode.com/problems/binary-tree-level-order-traversal-ii/)                       | [Link](./lib/medium/107_binary_tree_level_order_traversal_ii.rb)                       |
+| 109. Convert Sorted List to Binary Search Tree                  | [Link](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)                  | [Link](./lib/medium/109_convert_sorted_list_to_binary_search_tree.rb)                  |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index 5253914b..766079ae 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 = '6.4.0'
+  s.version = '6.4.1'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/109_convert_sorted_list_to_binary_search_tree.rb b/lib/medium/109_convert_sorted_list_to_binary_search_tree.rb
new file mode 100644
index 00000000..aa38d6ec
--- /dev/null
+++ b/lib/medium/109_convert_sorted_list_to_binary_search_tree.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require_relative '../common/binary_tree'
+require_relative '../common/linked_list'
+
+# https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/
+# @param {ListNode} head
+# @return {TreeNode}
+def sorted_list_to_bst(head)
+  return unless head
+
+  middle = middle(head)
+  node = ::TreeNode.new(middle.val)
+
+  return node if head == middle
+
+  node.left = sorted_list_to_bst(head)
+  node.right = sorted_list_to_bst(middle.next)
+
+  node
+end
+
+# public TreeNode sortedListToBST(ListNode head) {
+#   if (head == null) {
+#       return null;
+#   }
+#   ListNode middle = middle(head);
+#   TreeNode node = new TreeNode(middle.val);
+#   if (head == middle) {
+#       return node;
+#   }
+#   node.left = sortedListToBST(head);
+#   node.right = sortedListToBST(middle.next);
+#   return node;
+# }
+
+private
+
+# @param {ListNode} node
+# @return {ListNode}
+def middle(node)
+  fast = node
+  slow = node
+  prev = node
+
+  while !fast.nil? && !fast.next.nil?
+    prev = slow
+    slow = slow.next
+    fast = fast.next.next
+  end
+
+  prev.next = nil unless prev.nil?
+
+  slow
+end
diff --git a/test/medium/test_109_convert_sorted_list_to_binary_search_tree.rb b/test/medium/test_109_convert_sorted_list_to_binary_search_tree.rb
new file mode 100644
index 00000000..16b3cde5
--- /dev/null
+++ b/test/medium/test_109_convert_sorted_list_to_binary_search_tree.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/common/linked_list'
+require_relative '../../lib/medium/109_convert_sorted_list_to_binary_search_tree'
+require 'minitest/autorun'
+
+class ConvertSortedListToBinarySearchTreeTest < ::Minitest::Test
+  def test_default
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          0,
+          ::TreeNode.new(
+            -3,
+            ::TreeNode.new(-10),
+            nil
+          ),
+          ::TreeNode.new(
+            9,
+            ::TreeNode.new(5),
+            nil
+          )
+        ),
+        sorted_list_to_bst(
+          ::ListNode.from_array(
+            [-10, -3, 0, 5, 9]
+          )
+        )
+      )
+    )
+    assert(
+      ::TreeNode.are_equals(
+        nil,
+        sorted_list_to_bst(nil)
+      )
+    )
+  end
+end