{ "data": { "question": { "questionId": "2646", "questionFrontendId": "2583", "categoryTitle": "Algorithms", "boundTopicId": 2143004, "title": "Kth Largest Sum in a Binary Tree", "titleSlug": "kth-largest-sum-in-a-binary-tree", "content": "
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.
\n\nReturn 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.
\n\n\n
Example 1:
\n\n\nInput: root = [5,8,9,2,1,3,7,4,6], k = 2\nOutput: 13\nExplanation: The level sums are the following:\n- Level 1: 5.\n- Level 2: 8 + 9 = 17.\n- Level 3: 2 + 1 + 3 + 7 = 13.\n- Level 4: 4 + 6 = 10.\nThe 2nd largest level sum is 13.\n\n\n
Example 2:
\n\n\nInput: root = [1,2,null,3], k = 1\nOutput: 3\nExplanation: The largest level sum is 3.\n\n\n
\n
Constraints:
\n\nn
.2 <= n <= 105
1 <= Node.val <= 106
1 <= k <= n
给你一棵二叉树的根节点 root
和一个正整数 k
。
树中的 层和 是指 同一层 上节点值的总和。
\n\n返回树中第 k
大的层和(不一定不同)。如果树少于 k
层,则返回 -1
。
注意,如果两个节点与根节点的距离相同,则认为它们在同一层。
\n\n\n\n
示例 1:
\n\n\n\n\n输入:root = [5,8,9,2,1,3,7,4,6], k = 2\n输出:13\n解释:树中每一层的层和分别是:\n- Level 1: 5\n- Level 2: 8 + 9 = 17\n- Level 3: 2 + 1 + 3 + 7 = 13\n- Level 4: 4 + 6 = 10\n第 2 大的层和等于 13 。\n\n\n
示例 2:
\n\n\n\n\n输入:root = [1,2,null,3], k = 1\n输出:3\n解释:最大的层和是 3 。\n\n\n
\n\n
提示:
\n\nn
2 <= n <= 105
1 <= Node.val <= 106
1 <= k <= n
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