一题一句:注意维护值和返回值是不同的,注意用LinkedList传参数确保全局维护
/**
* 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 maxPathSum(TreeNode root) {
int[] res = new int[1];
res[0] = Integer.MIN_VALUE;
helper(res,root);
return res[0];
}
public int helper(int[] res, TreeNode node){
if (node == null)
return 0;
int L = helper(res,node.left);
int R = helper(res,node.right);
L = Math.max(L,0);
R = Math.max(R,0);
res[0] = Math.max(res[0], R + L + node.val);
return Math.max(L,R) + node.val;
}
}