/**
* 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;
}
int helper(TreeNode root) {
if (root == null) return 0;
int left = Math.max(helper(root.left), 0);
int right = Math.max(helper(root.right), 0);
max = Math.max(max, root.val + left + right);
return root.val + Math.max(left, right);
}
}