leetcode 124. Binary Tree Maximum Path Sum ----- java

Given a 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 does not need to go through the root.

For example:
Given the below binary tree,

       1
      / \
     2   3

 

Return 6.

 

 

求最大路径。

就是记录两个结果。

 

/**
 * 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) {
        if( root == null)
            return 0;
        long result[] = helper(root);
        

        return (int)Math.max(result[0], result[1]);
    }

    public long[] helper(TreeNode node){
        long[] result = new long[2];
        result[0] = Integer.MIN_VALUE;
        result[1] = Integer.MIN_VALUE;
        if( node == null )
            return result;
        result[0] = node.val;
        result[1] = node.val;
        if( node.left == null && node.right == null)
            return result;

        long[] num1 = helper(node.left);
        long[] num2 = helper(node.right);

        result[0] = Math.max(Math.max(num1[0],num2[0])+node.val,node.val);
        result[1] = Math.max(Math.max(Math.max(Math.max(Math.max(num1[1],num2[1]),num1[0]+num2[0]+node.val),num1[0]+node.val),
                    num2[0]+node.val),node.val);

        return result;
    }
}