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;
    }
};