129. Sum Root to Leaf Numbers java solutions

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.

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 1 /**
 2  * Definition for a binary tree node.
 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     int sum = 0;
12     public int sumNumbers(TreeNode root) {
13         if(root == null) return 0;
14         findSum(root,0);
15         return sum;
16     }
17
18     public void findSum(TreeNode root,int tmp){
19         if(root.left == null && root.right == null){
20             sum += 10*tmp + root.val;
21             return;
22         }
23         if(root.left != null) findSum(root.left, 10*tmp + root.val);
24
25         if(root.right != null) findSum(root.right, 10*tmp + root.val);
26     }
27 }