# 124. Binary Tree Maximum Path Sum

Given a non-empty 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.

Example 1:

``````Input: [1,2,3]

1
/ \
2   3

Output: 6
``````

Example 2:

``````Input: [-10,9,20,null,null,15,7]

-10
/ \
9  20
/  \
15   7

Output: 42
``````

``````    4
/ \
11 13
/ \
7   2
``````

``````class Solution {
public:
int maxPathSum(TreeNode* root) {
int res = INT_MIN;
helper(root, res);
return res;
}
int helper(TreeNode* node, int& res) {
if (!node) return 0;
int left = max(helper(node->left, res), 0);
int right = max(helper(node->right, res), 0);
res = max(res, left + right + node->val);
return max(left, right) + node->val;
}
};
``````

Github 同步地址：

https://github.com/grandyang/leetcode/issues/124

Path Sum

Sum Root to Leaf Numbers

Path Sum IV

Longest Univalue Path

https://leetcode.com/problems/binary-tree-maximum-path-sum/

https://leetcode.com/problems/binary-tree-maximum-path-sum/discuss/39775/Accepted-short-solution-in-Java

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