Sum Root to Leaf Numbers

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.

 

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