【二叉树(DFS)- LeetCode】124. 二叉树中的最大路径和

题目：

 124. 二叉树中的最大路径和

题解

DFS

/*** 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 {
private:int maxSum = INT_MIN;
public:int maxGain(TreeNode* node){if(node == nullptr){return 0;}// 子树递归计算贡献值，如果是负数的则不选择，也就是0int l = max(maxGain(node->left), 0);int r = max(maxGain(node->right), 0);int tmp_sum = l + r + node->val;maxSum = max(tmp_sum, maxSum);return node->val+max(l,r);}int maxPathSum(TreeNode* root) {maxGain(root);return maxSum;}
};