题解 | #字符串加密#

#include <iostream>
#include <unordered_set>
using namespace std;

int main() {
    string old_alphabet = "abcdefghijklmnopqrstuvwxyz";
    string new_alphabet, key, plain, cipher;//分别表示新字母表、密钥、明文、密文
    cin >> key >> plain;
    //删除密钥中重复的字符
    unordered_set<char> Set;
    for(int i = 0; i < key.length(); i++){
        for(int j = 0; j < old_alphabet.length(); j++){//从旧字母表中删除密钥中已有的字符
            if(old_alphabet[j] == key[i]){
                old_alphabet.erase(j, 1);
                break;
            }
        }
        if(Set.count(key[i]) != 0){ 
            key.erase(i--, 1);
        }
        Set.insert(key[i]);
    }
    //组合新字母表
    new_alphabet = key + old_alphabet;

    for(int i = 0; i < plain.length(); i++){
        cipher += new_alphabet[plain[i] - 'a'];
    }
    cout << cipher << endl;
    return 0;

}