LeetCode Letter Combinations of a Phone Number 电话号码组合

题意：给一个电话号码，要求返回所有在手机上按键的组合，组合必须由键盘上号码的下方的字母组成。

思路：尼玛，一直RE，题意都不说0和1怎么办。DP解决。

 class Solution {
 public:
     vector<string> ans;
     string str;

     void DFS(const string sett[], int siz, string t )
     {
         int n=str[siz]-'';
         if(siz==str.size()){ans.push_back( t );return ;}
         for(int i=; i<sett[n].size(); i++)    DFS(sett, siz+, t+sett[n][i] );
     }

     vector<string> letterCombinations(string digits) {
         if(digits.empty())  return vector<string> ();
         str=digits;
         const string mapp[]={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
         DFS(mapp, , "");
         return ans;
     }
 };

AC代码