(C++)电话号码的字母组合

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本题使用递归，该题不做解释

class Solution {
public:
    string str[10] = {"","","abc","def","ghi","jkl",
                        "mno","pqrs","tuv","wxyz"};

    void Conbine(vector<string>& vs, string& digits, int di, string Cbstr)
    {
        if(di == digits.size())
        {
            vs.push_back(Cbstr);
            return;
        }

        int num = digits[di] - '0';
        for(int i=0; i<str[num].size(); i++)
        {           
            Conbine(vs, digits, di+1, Cbstr+str[num][i]);
        }
    }


    vector<string> letterCombinations(string digits) 
    {
       
        vector<string> vs;

        if(digits == "")
            return vs;
            
        int di = 0;
        Conbine(vs, digits, di, "");

        return vs;
    }
};