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
Ref: https://zhuanlan.zhihu.com/p/77863151
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
int max = Integer.MIN_VALUE;
public int maxPathSum(TreeNode root) {
helper(root);
return max;
}
public int helper (TreeNode node) {
if (node == null) {
return 0;
}
int left = Math.max(helper(node.left), 0);
int right = Math.max(helper(node.right), 0);
max = Math.max(max, node.val + left + right);
return node.val + Math.max(left, right);
}
}
LeetCode - Binary Tree Maximum Path Sum
原文：https://www.cnblogs.com/incrediblechangshuo/p/12821756.html