Letter Combinations of a Phone Number

问题：链接

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.

解答：

DFS

参考：http://www.cnblogs.com/Rosanna/p/3416949.html

代码：

class Solution {public:    vector<string> letterCombinations(string digits) {string strlist[8] = {"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};        string result = "";        m_digits = digits;if(digits == ""){re_str.push_back("");return re_str;}        if(digits.size() == 0)            return re_str;        print(result, 0, strlist);        return re_str;    }    void print(string result, int i, string strlist[])    {        int num = m_digits[i] - '0';        if(i < m_digits.size())        {for(int j = 0; j < strlist[num-2].size(); ++j){print(result + strlist[num-2][j], i+1, strlist);}        }        else        {            re_str.push_back(result);        }    }private:    vector<string> re_str;    string m_digits;};