1161-maximum-level-sum-of-a-binary-tree.rb

# frozen_string_literal: true

# 1161. Maximum Level Sum of a Binary Tree
# https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree
# Medium

=begin
Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.

Return the smallest level x such that the sum of all the values of nodes at level x is maximal.

Example 1:
Input: root = [1,7,0,7,-8,null,null]
Output: 2
Explanation:
Level 1 sum = 1.
Level 2 sum = 7 + 0 = 7.
Level 3 sum = 7 + -8 = -1.
So we return the level with the maximum sum which is level 2.

Example 2:
Input: root = [989,null,10250,98693,-89388,null,null,null,-32127]
Output: 2

Constraints:
The number of nodes in the tree is in the range [1, 104].
-105 <= Node.val <= 105
=end

# Definition for a binary tree node.
# class TreeNode
#     attr_accessor :val, :left, :right
#     def initialize(val = 0, left = nil, right = nil)
#         @val = val
#         @left = left
#         @right = right
#     end
# end
# @param {TreeNode} root
# @return {Integer}
def max_level_sum(root)
  return 0 if root.nil?
  queue = [root]
  max_sum = -1000000
  max_level = level = 0
  while queue.any?
    size = queue.size
    sum = 0
    level += 1
    size.times {
      node = queue.shift
      sum += node.val
      queue.push(node.left) if node.left
      queue.push(node.right) if node.right
    }
    if max_sum < sum
      max_sum = sum
      max_level = level
    end
  end
  max_level
end