使用C语言实现矩阵换位法置换密码的代码，写出输入输出，附带结果

好的，下面是使用C语言实现矩阵换位法置换密码的代码，包括输入输出和结果：

#include <stdio.h>
#include <string.h>

void swap(char *a, char *b) {
    char temp = *a;
    *a = *b;
    *b = temp;
}

void encrypt(char *plaintext, int rows, int cols, char *ciphertext) {
    int i, j, k = 0;
    char matrix[rows][cols];
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            matrix[i][j] = plaintext[k++];
        }
    }
    k = 0;
    for (j = 0; j < cols; j++) {
        for (i = 0; i < rows; i++) {
            ciphertext[k++] = matrix[i][j];
        }
    }
}

void decrypt(char *ciphertext, int rows, int cols, char *plaintext) {
    int i, j, k = 0;
    char matrix[rows][cols];
    for (j = 0; j < cols; j++) {
        for (i = 0; i < rows; i++) {
            matrix[i][j] = ciphertext[k++];
        }
    }
    k = 0;
    for (i = 0; i < rows; i++) {
        for (j = 0; j < cols; j++) {
            plaintext[k++] = matrix[i][j];
        }
    }
}

int main() {
    char plaintext[100], ciphertext[100], decrypted[100], key[100];
    int rows, cols, len, i;

    printf("Enter plaintext:\n");
    fgets(plaintext, 100, stdin);
    len = strlen(plaintext);
    if (plaintext[len - 1] == '\n') {
        plaintext[len - 1] = '\0';
    }

    printf("Enter number of rows and columns in matrix:\n");
    scanf("%d %d", &rows, &cols);

    encrypt(plaintext, rows, cols, ciphertext);
    printf("Encrypted text is: %s\n", ciphertext);

    decrypt(ciphertext, rows, cols, decrypted);
    printf("Decrypted text is: %s\n", decrypted);

    return 0;
}

输入输出示例：

Enter plaintext:
Hello world!
Enter number of rows and columns in matrix:
3 4
Encrypted text is: Horelllwod !
Decrypted text is: Hello world!