Sum Root to Leaf Numbers <leetcode>

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.

算法：本体很简单，二叉树的遍历，主要是考虑一些细节，代码如下：

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
 struct node
 {
     TreeNode *root;
     int val;
 };
class Solution {
public:
    int result;
    bool k=true;
    int sumNumbers(TreeNode *root) {
        if(NULL==root)  return 0;
        result=0;
        vector<node>  temp;
        temp.clear();
        doit(root,temp);
        return result;
    }
    
    void doit(TreeNode* &root,vector<node>  temp)
    {
        if(NULL==root->left&&NULL==root->right)
        {
            if(k)  result+=root->val;
            
            else result+=temp.back().val*10+root->val;
            return;
        }
        else
        {
            node n;
            if(k) 
            {
                n.val=root->val;
                k=false;
            }
            else   n.val=temp.back().val*10+root->val;
            n.root=root;
            temp.push_back(n);
            if(NULL!=root->left)
            {
              doit(root->left,temp);
            }
            if(NULL!=root->right)
            {
                doit(root->right,temp);
            }
        }
    }
};