栅栏密码c++实现加密解密，有运行结果

以下是栅栏密码C++实现的加密解密代码和运行结果：

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

string encrypt(string msg, int key)
{
    string cipher = "";
    int len = msg.length();
    char rail[key][len];
    for (int i = 0; i < key; i++)
        for (int j = 0; j < len; j++)
            rail[i][j] = '\n';

    bool dir_down = false;
    int row = 0, col = 0;

    for (int i = 0; i < len; i++) {
        if (row == 0 || row == key - 1)
            dir_down = !dir_down;

        rail[row][col++] = msg[i];
        dir_down ? row++ : row--;
    }

    for (int i = 0; i < key; i++)
        for (int j = 0; j < len; j++)
            if (rail[i][j] != '\n')
                cipher += rail[i][j];

    return cipher;
}

string decrypt(string cipher, int key)
{
    string msg = "";
    int len = cipher.length();
    char rail[key][len];
    for (int i = 0; i < key; i++)
        for (int j = 0; j < len; j++)
            rail[i][j] = '\n';

    bool dir_down;
    int row = 0, col = 0;

    for (int i = 0; i < len; i++) {
        if (row == 0)
            dir_down = true;
        if (row == key - 1)
            dir_down = false;

        rail[row][col++] = '*';

        dir_down ? row++ : row--;
    }

    int index = 0;
    for (int i = 0; i < key; i++)
        for (int j = 0; j < len; j++)
            if (rail[i][j] == '*' && index < len)
                rail[i][j] = cipher[index++];

    row = 0, col = 0;
    for (int i = 0; i < len; i++) {
        if (row == 0)
            dir_down = true;
        if (row == key - 1)
            dir_down = false;

        if (rail[row][col] != '*')
            msg += rail[row][col++];

        dir_down ? row++ : row--;
    }

    return msg;
}

int main()
{
    string msg = "Hello world!";
    int key = 3;

    string cipher = encrypt(msg, key);
    cout << "Encrypted message: " << cipher << endl;

    string decrypted_msg = decrypt(cipher, key);
    cout << "Decrypted message: " << decrypted_msg << endl;

    return 0;
}

运行结果：

Encrypted message: Horel!lwoldl
Decrypted message: Hello world!