Merge pull request #790 from fartem/508_Most_Frequent_Subtree_Sum

2024-12-03 v. 7.1.9: added "508. Most Frequent Subtree Sum"

Author: fartem

README.md

@@ -584,3 +584,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 468. Validate IP Address                                        | [Link](https://leetcode.com/problems/validate-ip-address/)                                        | [Link](./lib/medium/468_validate_ip_address.rb)                                        | [Link](./test/medium/test_468_validate_ip_address.rb)                                        |
 | 474. Ones and Zeroes                                            | [Link](https://leetcode.com/problems/ones-and-zeroes/)                                            | [Link](./lib/medium/474_ones_and_zeroes.rb)                                            | [Link](./test/medium/test_474_ones_and_zeroes.rb)                                            |
 | 503. Next Greater Element II                                    | [Link](https://leetcode.com/problems/next-greater-element-ii/)                                    | [Link](./lib/medium/503_next_greater_element_ii.rb)                                    | [Link](./test/medium/test_503_next_greater_element_ii.rb)                                    |
+| 508. Most Frequent Subtree Sum                                  | [Link](https://leetcode.com/problems/most-frequent-subtree-sum/)                                  | [Link](./lib/medium/508_most_frequent_subtree_sum.rb)                                  | [Link](./test/medium/test_508_most_frequent_subtree_sum.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 = '7.1.8'
+  s.version = '7.1.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/508_most_frequent_subtree_sum.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+$freq = 0
+
+# https://leetcode.com/problems/most-frequent-subtree-sum/
+# @param {TreeNode} root
+# @return {Integer[]}
+def find_frequent_tree_sum(root)
+  $freq = 0
+
+  values = {}
+  fill_values_from_sub_tree(root, values)
+
+  most_freq = []
+  values.entries.each { |key, value| most_freq << key if value == $freq }
+
+  most_freq
+end
+
+private
+
+# @param {TreeNode} node
+# @param {Set<Integer, Integer>} values
+# @return {Integer}
+def fill_values_from_sub_tree(node, values)
+  return 0 unless node
+
+  left = fill_values_from_sub_tree(node.left, values)
+  right = fill_values_from_sub_tree(node.right, values)
+  sum = node.val + left + right
+
+  values[sum] = values.fetch(sum, 0) + 1
+  $freq = [$freq, values[sum]].max
+
+  sum
+end

test/medium/test_508_most_frequent_subtree_sum.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/508_most_frequent_subtree_sum'
+require 'minitest/autorun'
+
+class MostFrequentSubtreeSumTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      [2, -3, 4],
+      find_frequent_tree_sum(
+        ::TreeNode.new(
+          5,
+          ::TreeNode.new(2),
+          ::TreeNode.new(-3)
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      [2],
+      find_frequent_tree_sum(
+        ::TreeNode.new(
+          5,
+          ::TreeNode.new(2),
+          ::TreeNode.new(-5)
+        )
+      )
+    )
+  end
+end