LeetCode 二叉树中的最大路径和(二叉树)(DFS)

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/**
 * 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(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int imax = INT_MIN;
    int maxpath(TreeNode* root) {
        if (root == nullptr) {
            return 0;
        }

        int left = max(0, maxpath(root->left));
        int right = max(0, maxpath(root->right));
        /*二叉树的后序遍历*/
        imax = max(imax, left + right + root->val);
        return max(left, right) + root->val;
    }
    int maxPathSum(TreeNode* root) {
        maxpath(root);
        return imax;
    }
};