[LeetCode]Sum Root to Leaf Numbers

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.

递归深搜，一类题。

/**
 * 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:
    void dfs(TreeNode* root,int num,int& result)
    {
        num=num*10+root->val;
        if(root->left==NULL && root->right==NULL)
        {
            result+=num;
            return;
        }
        if(root->left) dfs(root->left,num,result);
        if(root->right) dfs(root->right,num,result);
    }
    int sumNumbers(TreeNode* root) {
        if(!root) return 0;
        int num=0,result=0;
        dfs(root,num,result);
        return result;
    }
};