/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public int max = Integer.MIN_VALUE;// not 0!!!! public int maxPathSum(TreeNode root) { oneSide(root); return max; } public int oneSide(TreeNode root){ if(root == null) return 0; int left = Math.max(0, oneSide(root.left)); int right = Math.max(0, oneSide(root.right)); max = Math.max(max, root.val + left + right); return root.val + Math.max(left, right); } }