2d arrays

#include<stdio.h>
#include<stdlib.h>

/*
1 2 3
4 5 6
7 8 9
==>
9 6 3
8 5 2
7 4 1


n = 3

i j      x y
0 0  <-> 2 2
0 1  <-> 1 2
1 0  <-> 2 1

x = n - j -1
y = n - i -1
*/

void mirror_flattened(int *t, int n)
{
    int i, j;

    for(i = 0; i < n - 1; ++i)
    {
        for(j = 0; j < n - i; ++j)
        {
            int x = n - j - 1, y = n - i - 1, tmp;
            tmp = t[i * n +  j];
            t[i * n + j] = t[x * n + y];
            t[x * n + y] = tmp;
        }
    }
}



void mirror_jagged(int **t, int n)
{
    int i, j;

    for(i = 0; i < n - 1; ++i)
    {
        for(j = 0; j < n - i; ++j)
        {
            int x = n - j - 1, y = n - i - 1, tmp;
            tmp = t[i][j];
            t[i][j] = t[x][y];
            t[x][y] = tmp;
        }
    }
}


int main()
{
    int M[3][3] = { {1,2,3},
                    {4,5,6},
                    {7,8,9}};
    int **t, i, j, x;
    t = (int**) malloc(3*sizeof(int*));

    x = 1;
    for(i = 0; i < 3; ++i)
    {
        t[i] = (int*) malloc(3*sizeof(int));
        for(j = 0; j < 3; ++j)
            t[i][j] = x++;
    }

    mirror_flattened((int*)M,3);

    for(i = 0; i < 3; ++i)
    {
        for(j = 0; j < 3; ++j)
            printf("%d ", M[i][j]);
        printf("\n");
    }
    return 0;
}