LeetCode: Sum Root to Leaf Numbers 解题报告

 1 /**
 2  * Definition for binary tree
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 public class Solution {
11     public int sumNumbers(TreeNode root) {
12         return dfs(root, 0);
13     }
14     
15     public int dfs(TreeNode root, int pre) {
16         if (root == null) {
17             return 0;
18         }
19         
20         int cur = pre * 10 + root.val;
21         if (root.left == null && root.right == null) {
22             return cur;
23         }
24         
25         return dfs(root.left, cur) + dfs(root.right, cur);
26     }
27 }