c语言凯撒密码前后端代码

Sure! Here's an example of the Caesar Cipher encryption and decryption code in C language:

#include <stdio.h>

// Function to encrypt the message using Caesar Cipher
void encrypt(char message[], int key) {
    char ch;
    int i;

    for(i = 0; message[i] != '\0'; ++i) {
        ch = message[i];

        if(ch >= 'a' && ch <= 'z') {
            ch = ch + key;

            if(ch > 'z') {
                ch = ch - 'z' + 'a' - 1;
            }

            message[i] = ch;
        }
        else if(ch >= 'A' && ch <= 'Z') {
            ch = ch + key;

            if(ch > 'Z') {
                ch = ch - 'Z' + 'A' - 1;
            }

            message[i] = ch;
        }
    }

    printf("Encrypted message: %s\n", message);
}

// Function to decrypt the message using Caesar Cipher
void decrypt(char message[], int key) {
    char ch;
    int i;

    for(i = 0; message[i] != '\0'; ++i) {
        ch = message[i];

        if(ch >= 'a' && ch <= 'z') {
            ch = ch - key;

            if(ch < 'a') {
                ch = ch + 'z' - 'a' + 1;
            }

            message[i] = ch;
        }
        else if(ch >= 'A' && ch <= 'Z') {
            ch = ch - key;

            if(ch < 'A') {
                ch = ch + 'Z' - 'A' + 1;
            }

            message[i] = ch;
        }
    }

    printf("Decrypted message: %s\n", message);
}

int main() {
    char message[100];
    int key;

    printf("Enter a message: ");
    scanf("%[^\n]s", message);

    printf("Enter key: ");
    scanf("%d", &key);

    encrypt(message, key);
    decrypt(message, key);

    return 0;
}

In this code, the `encrypt` function takes a message and a key as input and encrypts the message using the Caesar Cipher algorithm. The `decrypt` function takes an encrypted message and the same key as input and decrypts the message.

The `main` function prompts the user to enter a message and a key, and then calls the `encrypt` and `decrypt` functions accordingly. Finally, it prints the encrypted and decrypted messages.

Please note that this is a basic implementation of the Caesar Cipher and may not include error handling or additional features.