凯撒密码算法c++实现

以下是凯撒密码算法的C++实现：

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

string encrypt(string plaintext, int k) {
    string ciphertext = "";
    for (int i = 0; i < plaintext.length(); i++) {
        if (isalpha(plaintext[i])) {
            char c = plaintext[i];
            if (isupper(c)) {
                c = (c + k - 'A') % 26 + 'A';
            } else {
                c = (c + k - 'a') % 26 + 'a';
            }
            ciphertext += c;
        } else {
            ciphertext += plaintext[i];
        }
    }
    return ciphertext;
}

int main() {
    string plaintext;
    int k;
    cout << "请输入明文：";
    getline(cin, plaintext);
    cout << "请输入密钥：";
    cin >> k;
    string ciphertext = encrypt(plaintext, k);
    cout << "加密后的密文为：" << ciphertext << endl;
    return 0;
}