题解 | #牛名生成器#

#include <unordered_map>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param digits string字符串 
     * @return string字符串vector
     */

    vector<string> ans;

    void dfs(string digits, int start, string str, unordered_map<char, string> u_m)
    {
        int len = digits.size();
        
        if(start==len)
        {
            ans.emplace_back(str);
            return;
        }

        char num = digits[start];
        string t_str = u_m[num];
        for(int i=0; i<t_str.size(); ++i)
            dfs(digits, start+1, str+t_str[i], u_m);

        return;
    }


    vector<string> letterCombinations(string digits) {
        // write code here
        unordered_map<char, string> u_m = {{'2', "abc"}, {'3', "def"}, {'4', "ghi"}, {'5', "jkl"}, {'6', "mno"}, {'7', "pqrs"}, {'8', "tuv"}, {'9', "wxyz"}};

        string str = "";
        dfs(digits, 0, str, u_m);

        return ans;
    }
};