1 //New
2 class Solution {
3 public int sumNumbers(TreeNode root) {
4 if(root == null) return 0;
5 return dfs(root, 0);
6
7 }
8
9 public int dfs(TreeNode root, int sum) {
10 if(root == null) return 0;
11 if(root.left == null && root.right == null) {
12 return sum*10 + root.val;
13 }else {
14 return dfs(root.left, sum*10 + root.val) + dfs(root.right, sum*10 + root.val);
15 }
16
17 }
18 }
19
20
21
22
23
24 //Old
25 class Solution {
26 int sum = 0;
27 public int sumNumbers(TreeNode root) {
28 if(root == null) return 0;
29 dfs(root, new StringBuilder());
30 return sum;
31
32 }
33
34 public void dfs(TreeNode root, StringBuilder sb) {
35 if(root == null) return;
36 if(root.left == null && root.right == null) {
37 sb.append(root.val);
38 sum += Integer.parseInt(sb.toString());
39 sb.deleteCharAt(sb.length() - 1);
40 }else {
41 sb.append(root.val);
42 dfs(root.left, sb);
43 dfs(root.right, sb);
44 sb.deleteCharAt(sb.length() - 1);
45 }
46
47 }
48 }
