#2583 - Kth Largest Sum in a Binary Tree

Medium • View on LeetCode • View on GitHub

Sorting Tree Breadth-First Search Binary Tree

Problem Description

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.

Solution

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} k
 * @return {number}
 */
var kthLargestLevelSum = function(root, k) {
  const levelSums = [];
  const queue = [root];

  while (queue.length) {
    let levelSize = queue.length;
    let levelSum = 0;

    while (levelSize--) {
      const node = queue.shift();
      levelSum += node.val;
      if (node.left) queue.push(node.left);
      if (node.right) queue.push(node.right);
    }

    levelSums.push(levelSum);
  }

  if (levelSums.length < k) return -1;

  return levelSums.sort((a, b) => b - a)[k - 1];
};