2025-01-21 v. 8.2.0: added "988. Smallest String Starting From Leaf"

README.md

@@ -652,6 +652,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 979. Distribute Coins in Binary Tree                             | [Link](https://leetcode.com/problems/distribute-coins-in-binary-tree/)                             | [Link](./lib/medium/979_distribute_coins_in_binary_tree.rb)                             | [Link](./test/medium/test_979_distribute_coins_in_binary_tree.rb)                             |
 | 981. Time Based Key-Value Store                                  | [Link](https://leetcode.com/problems/time-based-key-value-store/)                                  | [Link](./lib/medium/981_time_based_key_value_store.rb)                                  | [Link](./test/medium/test_981_time_based_key_value_store.rb)                                  |
 | 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)                          |
 | 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 = '8.1.9'
+  s.version = '8.2.0'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/988_smallest_string_starting_from_leaf.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/smallest-string-starting-from-leaf/
+# @param {TreeNode} root
+# @return {String}
+def smallest_from_leaf(root)
+  @result = '~'
+  find_smallest_string_staring_from_leaf(root, '')
+
+  @result
+end
+
+private
+
+# @param {TreeNode} root
+# @param {Array} curr
+# @return {Void}
+def find_smallest_string_staring_from_leaf(root, curr)
+  return unless root
+
+  c = (root.val + 97).chr
+  new_curr = c + curr
+
+  if !root.left && !root.right
+    @result = new_curr if @result > new_curr
+  else
+    find_smallest_string_staring_from_leaf(root.left, new_curr)
+    find_smallest_string_staring_from_leaf(root.right, new_curr)
+  end
+end

test/medium/test_988_smallest_string_starting_from_leaf.rb

@@ -0,0 +1,75 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/988_smallest_string_starting_from_leaf'
+require 'minitest/autorun'
+
+class SmallestStringStartingFromLeafTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      'dba',
+      smallest_from_leaf(
+        ::TreeNode.new(
+          0,
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(3),
+            ::TreeNode.new(4)
+          ),
+          ::TreeNode.new(
+            2,
+            ::TreeNode.new(3),
+            ::TreeNode.new(4)
+          )
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      'adz',
+      smallest_from_leaf(
+        ::TreeNode.new(
+          25,
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(1),
+            ::TreeNode.new(3)
+          ),
+          ::TreeNode.new(
+            3,
+            ::TreeNode.new(0),
+            ::TreeNode.new(2)
+          )
+        )
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      'abc',
+      smallest_from_leaf(
+        ::TreeNode.new(
+          2,
+          ::TreeNode.new(
+            2,
+            nil,
+            ::TreeNode.new(
+              1,
+              ::TreeNode.new(0),
+              nil
+            )
+          ),
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(0),
+            nil
+          )
+        )
+      )
+    )
+  end
+end