leetcode[129]Sum Root to Leaf Numbers

题目要求

Given a binary tree containing digits from 0-9
only, each root-to-leaf path could represent a number.
An example is the root-to-leaf path 1->2->3
which represents the number 123.
Find the total sum of all root-to-leaf numbers.
For example,
1
/ \
2 3

The root-to-leaf path 1->2
represents the number 12.The root-to-leaf path 1->3 represents the number 13.
Return the sum = 12 + 13 = 25.

代码实现

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    int res = 0;
    public int sumNumbers(TreeNode root) {
        if(root == null){
            return 0;
        }
        sum(root,0);
        return res;
        
    }
    public void sum(TreeNode node,int tmp){
        
        tmp = tmp * 10 + node.val;
        if(node.left==null&&node.right==null){ 
            res += tmp;
        }
        if(node.left!= null){
            sum(node.left,tmp);
           
        }
        if(node.right!=null){
            sum(node.right,tmp);
            
        }
       
    }
}