Rotate square matrix in-place

#include <bits/stdc++.h>
using namespace std;

const int N = 100;

void print(int a[N], int n) {
    printf("[");
    for (int i = 0; i < n; ++i) {
        printf("%s%2d", i > 0 ? ", " : "", a[i]);
    }
    printf("]");
}

void print(int a[N][N], int n) {
    printf("[");
    for (int i = 0; i < n; ++i) {
        if (i > 0) printf(" ");
        print(a[i], n);
        printf("%s", i+1 < n ? ",\n" : "");
    }
    printf("]\n");
}

void mirror_horizontally(int a[N][N], int n) {
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n/2; ++j) {
            swap(a[i][j], a[i][n-1-j]);
        }
    }
}

void mirror_along_main_diagonal(int a[N][N], int n) {
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < i; ++j) {
            swap(a[i][j], a[j][i]);
        }
    }
}

void rotate_clockwise(int a[N][N], int n) {
    mirror_along_main_diagonal(a, n);
    mirror_horizontally(a, n);
}

int main() {
    int a[N][N];
    int n = 4;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            a[i][j] = i*n + j;
        }
    }
    print(a, n);
    mirror_horizontally(a, n);
    print(a, n);
    mirror_horizontally(a, n);
    print(a, n);
    mirror_along_main_diagonal(a, n);
    print(a, n);
    mirror_along_main_diagonal(a, n);
    print(a, n);
    rotate_clockwise(a, n);
    print(a, n);
    rotate_clockwise(a, n);
    print(a, n);
    rotate_clockwise(a, n);
    print(a, n);
    rotate_clockwise(a, n);
    print(a, n);
}