leetcode个人题解——#17 Letter Combinations of a Phone Number

思路：用深搜遍历九宫格字符串，一开始做的时候发生了引用指向空地址的问题，后来发现是vector不能直接=赋值。

class Solution {

public:

    int len;

    string map[]={"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};

    void search(int pos, string res, vector<string>& a, string digits){

        if(pos == len) return;

        string s = map[digits[pos] - ''];

        for (int i = ;i < s.size(); i++)

        {

            if(pos == len - )a.push_back(res + s[i]);

            else search(pos + , res + s[i], a, digits);

        }

    }

    vector<string> letterCombinations(string digits) {

        vector<string> ans;

        len = digits.size();

        if(len == )return ans;

        search(,"",ans,digits);

        return ans;

    }

};