leetcode-----124. 二叉树中的最大路径和

• 链接：https://leetcode-cn.com/problems/binary-tree-maximum-path-sum/

代码

/*
 * @lc app=leetcode.cn id=124 lang=cpp
 *
 * [124] 二叉树中的最大路径和
 * 枚举路径的最高点
 */

// @lc code=start
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int ans;
    int maxPathSum(TreeNode* root) {
        ans = INT_MIN;
        dfs(root);
        return ans;
    }

    int dfs(TreeNode* root) {
        if (!root) return 0;
        int left = max(0, dfs(root->left));
        int right = max(0, dfs(root->right));
        ans = max(ans, root->val + left + right);
        return root->val + max(left, right);
    }
};
// @lc code=end