题目

https://www.nowcoder.com/practice/da785ea0f64b442488c125b441a4ba4a?tpId=190&rp=1&ru=%2Fta%2Fjob-code-high-rd&qru=%2Fta%2Fjob-code-high-rd%2Fquestion-ranking

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 * }
 */

public class Solution {
    /**
     * 
     * @param root TreeNode类 
     * @return int整型
     */
    public static int maxValue;

    public int maxPathSum (TreeNode root) {
        // write code here
        maxValue = Integer.MIN_VALUE;
        getMaxPathSum(root);
        return maxValue;
    }
    public int getMaxPathSum(TreeNode root){
        if(root != null){
            int maxLeftValue = Math.max(0,getMaxPathSum(root.left));
            int maxRightValue = Math.max(0,getMaxPathSum(root.right));
            maxValue = Math.max(maxValue,maxLeftValue + root.val + maxRightValue);
            return Math.max(maxLeftValue , maxRightValue)+ root.val;
        }
        return 0;
    }
}