[LeetCode129]Sum Root to Leaf Numbers

题目：

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.

分类：Tree DFS 

代码：

 /**
  * Definition for a binary tree node.
  * struct TreeNode {
  *     int val;
  *     TreeNode *left;
  *     TreeNode *right;
  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
  * };
  */
 class Solution {
 public:
     int sumNumbers(TreeNode* root) {
         return DFS(root,);
     }

     int DFS(TreeNode* root, int sum)
     {
         if(!root)
             return ;
         int newSum = sum *  + root->val;
         if(!root->left && !root->right)
             return newSum;
         return DFS(root->left,newSum) + DFS(root->right,newSum);
     }
 };