2583-kth-largest-sum-in-a-binary-tree.rb

# frozen_string_literal: true

# 2583. Kth Largest Sum in a Binary Tree
# Medium
# https://leetcode.com/problems/kth-largest-sum-in-a-binary-tree

=begin
You are given the root of a binary tree and a positive integer k.
The level sum in the tree is the sum of the values of the nodes that are on the same level.
Return the kth largest level sum in the tree (not necessarily distinct). If there are fewer than k levels in the tree, return -1.
Note that two nodes are on the same level if they have the same distance from the root.

Example 1:
Input: root = [5,8,9,2,1,3,7,4,6], k = 2
Output: 13
Explanation: The level sums are the following:
- Level 1: 5.
- Level 2: 8 + 9 = 17.
- Level 3: 2 + 1 + 3 + 7 = 13.
- Level 4: 4 + 6 = 10.
The 2nd largest level sum is 13.

Example 2:
Input: root = [1,2,null,3], k = 1
Output: 3
Explanation: The largest level sum is 3.

Constraints:
* The number of nodes in the tree is n.
* 2 <= n <= 105
* 1 <= Node.val <= 106
* 1 <= k <= n
=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
# @param {Integer} k
# @return {Integer}
def kth_largest_level_sum(root, k)
  return -1 if root.nil?

  sums = []
  queue = [root]

  while !queue.empty?
    lvl_sum = 0
    size = queue.size

    size.times do
      node = queue.shift
      lvl_sum += node.val

      queue << node.left if node.left
      queue << node.right if node.right
    end

    sums << lvl_sum
  end

  return -1 if k > sums.size

  sums.sort.reverse[k - 1]
end