C++ 代码

class Solution {
public:
    string dict[8]={"abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
    vector<string> ans;
    string path;
    vector<string> letterCombinations(string digits) {
        if(!digits.size()) return vector<string>();
        dfs(digits,0);
        return ans;
    }
    void dfs(string & s,int n)
    {
        if(n==s.size())
        {
            ans.push_back(path);
            return ;
        }
        int ch=s[n]-'2';
        for(int i=0;i<dict[ch].size();i++)
        {
            string tmp=path;
            path+=dict[ch][i];
            dfs(s,n+1);
            path=tmp;
        }


    }
};