[Leetcode] 124. Binary Tree Maximum Path Sum
阿新 • • 發佈:2018-12-13
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
class Solution { public: int maxPathSum(TreeNode* root) { // root != nulllptr return maxPathSumHelper(root).first; } private: pair<int, int> maxPathSumHelper(TreeNode *root) { if (!root) return {INT_MIN, 0}; auto left = maxPathSumHelper(root->left); auto right = maxPathSumHelper(root->right); left.second = max(left.second, 0); right.second = max(right.second, 0); return {max(max(left.first, right.first), left.second + right.second + root->val), max(left.second, right.second) + root->val}; } };