題目

給定一個數字字串，返回數字所有可能表示的字母組合。
下面給出數字到字母的對映（和電話號碼一樣）。

輸入：數字字串 “23”
輸出：[“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”].

說明:
儘管上面的答案是按字典序排列的，但是你的答案可以是任何順序。

程式碼

class Solution {
public:
    vector<string> letterCombinations(string digits) {
        vector<string> s1,s2;
        map
 
<char,vector<string>> mp;
        mp['2']={"a","b","c"};
        mp['3']={"d","e","f"};
        mp['4']={"g","h","i"};
        mp['5']={"j","k","l"};
        mp['6']={"m","n","o"};
        mp['7']={"p","q","r","s"};
        mp['8']={"t","u","v"};
        mp['9']={"w","x","y","z"};
        for
 
(auto &ch:digits){
            int size=s1.size();
            auto &v=mp[ch];
            for(auto &s:v){
                for(int i=0;i<size;i++){
                    string tmp=s1[i]+s;
                    s2.push_back(tmp);
                }
                if(size==0) s2.push_back(s);
            }
            swap(s1,s2);
            s2.clear();
        }
        return
 
 s1;
    }
};

提交結果