题解 | #二叉树根节点到叶子节点的所有路径和#

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 int sumNumbers (TreeNode root) {
        // write code here
        int sum =0;
        if(root == null) return sum;
       return proorderSumNumber(root,sum);
    }
    public  int proorderSumNumber(TreeNode root,int sum){
        if(root == null) return 0;
        sum = sum * 10 + root.val;
        if(root.right == null && root.left == null) return sum;
        return  proorderSumNumber(root.left,sum) + proorderSumNumber(root.right,sum);
    }
}