[leetcode]_Sum Root to Leaf Numbers

 1     private int sum = 0;
 2     public int sumNumbers(TreeNode root) {
 3         dfs(root , 0);
 4         return sum;
 5     }
 6     public void dfs(TreeNode node , int tempSum){
 7         if(node == null) return ;
 8         
 9         tempSum = tempSum * 10 + node.val;
10         if(node.left == null && node.right == null)  {
11             sum += tempSum;
12             return;
13         }
14         
15         dfs(node.left , tempSum);
16         dfs(node.right , tempSum);
17     }