Binary Tree Maximum Path Sum

Binary Tree Maximum Path Sum

Given a binary tree, find the maximum path sum.

The path may start and end at any node in the tree.

求树的一点到另一点的最大路径，利用递归的方法，ans 在 左子树，右子树，root+左+右的最大中产生。

/** * Definition for binary tree * 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;      travel(root);      return ans;    }    int travel(TreeNode * root){        if(root == NULL) return 0;        int sum = root->val;        int leftsum = travel(root->left);        int rightsum = travel(root->right);        if(leftsum > 0) sum += leftsum;        if(rightsum > 0) sum += rightsum;        ans = max(ans,sum);        sum = max(leftsum,rightsum);        return root->val + (sum > 0 ? sum : 0);    }};