Leetcode 508. Most Frequent Subtree Sum (二叉树后序遍历好题)

最新推荐文章于 2025-12-24 17:58:28 发布

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最新推荐文章于 2025-12-24 17:58:28 发布 · 558 阅读

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文章介绍了解决给定二叉树中找到最频繁子树和的问题，利用后序遍历和map数据结构存储子树和及其频率，返回所有出现频率最高的子树和值。

Most Frequent Subtree Sum
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Given the root of a binary tree, return the most frequent subtree sum. If there is a tie, return all the values with the highest frequency in any order.

The subtree sum of a node is defined as the sum of all the node values formed by the subtree rooted at that node (including the node itself).

Example 1:

Input: root = [5,2,-3]
Output: [2,-3,4]
Example 2:

Input: root = [5,2,-5]
Output: [2]

Constraints:

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

解法1：用后序遍历！

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullpt