leetcode-Letter Combinations of a Phone Number

Given a digit string, return all possible letter combinations that the number could represent.

A mapping of digit to letters (just like on the telephone buttons) is given below.

Input:Digit string "23"Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

思路：DFS（参考其他人的思路才解决的。。。）

代码：

void DFS(string digits,string str,int dep,vector<string> &res,string *maptable)
{
if(dep == digits.length())
{
res.push_back(str);
return;
}
for(int i=0; i<maptable[digits[dep]-'0'].length();++i)
{
string temp=str;
temp+=maptable[digits[dep]-'0'][i];
DFS(digits,temp,dep+1,res,maptable);
}
}
vector<string> letterCombinations(string digits)
{
string maptable[]={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
string str="";
vector<string> res;

DFS(digits,str,0,res,maptable);
return res;
}