/**
* 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 maxPathSum(TreeNode* root) {
int res = INT_MIN;
helper(root, res);
return res;
}
int helper(TreeNode* root, int& res){
if(!root) return 0;
int left = max(helper(root->left, res), 0);
int right = max(helper(root->right, res), 0);
res = max(res, left+right+root->val);
return max(left, right)+root->val;
}
};
Path 构成 = left 弯曲path + root + right弯曲path