Binary Tree Maximum Path Sum

Desicription

Given a binary tree, find the maximum path sum.

For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path must contain at least one node and does not need to go through the root.

For example:
Given the below binary tree,

1
2
3
1
/ \
2 3

Return 6.

Solution

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/**
* 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 {
private:
int res = INT_MIN;
int getSonMax(TreeNode* cur) {
if(cur == NULL)
return 0;
int l = max(0, getSonMax(cur->left));
int r = max(0, getSonMax(cur->right));
res = max(res, l + r + cur->val);
return cur->val + max(l, r);
}
public:
int maxPathSum(TreeNode* root) {
getSonMax(root);
return res;
}
};