凯撒密码加密算法c++

以下是C++实现凯撒密码加密算法的代码：

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

string encrypt(string plaintext, int key) {
    string ciphertext = "";
    for (int i = 0; i < plaintext.length(); i++) {
        if (isalpha(plaintext[i])) {
            if (isupper(plaintext[i])) {
                ciphertext += char(int(plaintext[i] + key - 65) % 26 + 65);
            }
            else {
                ciphertext += char(int(plaintext[i] + key - 97) % 26 + 97);
            }
        }
        else {
            ciphertext += plaintext[i];        }
    }
    return ciphertext;
}

int main() {
    string plaintext = "hello world";
    int key = 3;
    string ciphertext = encrypt(plaintext, key);
    cout << "Plaintext: " << plaintext << endl;
    cout << "Ciphertext: " << ciphertext << endl;
    return 0;
}