Moving elements in 2d array for c -

so have 2d array filled random numbers .for example:

#define d 4  int main(void) { int a[d][d]; int primary[d], secondary[d]; size_t i, j;  srand(time(null));  /* fill array random numbers */ (i = 0; < d; i++)     (j = 0; j < d; j++)         a[i][j] = rand() % 100;  /* save diagonals */ (i = 0; < d; i++) {     primary[i] = a[i][i];     secondary[i] = a[d - (i + 1)][i]; 

how mirror horizontally diagonals?

for example:

1  0  0  2       0  3  4  0  0  5  6  0  7  0  0  8 

---

8  0  0  7  0  6  5  0  0  4  3  0  2  0  0  1 

task print main matrix , print matrix mirrored diagonals got no ideas how cycle should like.

i thought cycle rotating matrix 180 degrees loose positions of elements not included diagonals.

or can save diagonal , reverse somehow. here code matrix , diagonal should now.

hope help.

one of approaches following

#include <stdio.h>  #define n   4  int main(void)  {     int a[n][n] =     {         { 1,  0,  0,  2 },              { 0,  3,  4,  0 },         { 0,  5,  6,  0 },         { 7,  0,  0,  8 }     };            ( size_t = 0; < n; i++ )     {          ( size_t j = 0; j < n; j++ ) printf( "%d ", a[i][j] );         printf( "\n" );     }      printf( "\n" );      ( size_t = 0; < n * n / 2; i++ )     {         int tmp = a[i / n][i % n];         a[i / n][i % n] = a[(n * n - - 1) / n][(n * n - - 1) % n];         a[(n * n - - 1) / n][(n * n - - 1) % n] = tmp;     }      ( size_t = 0; < n; i++ )     {          ( size_t j = 0; j < n; j++ ) printf( "%d ", a[i][j] );         printf( "\n" );     }      printf( "\n" );      return 0; } 

the program output is

1 0 0 2  0 3 4 0  0 5 6 0  7 0 0 8   8 0 0 7  0 6 5 0  0 4 3 0  2 0 0 1  

the same can written using pointers. example

#include <stdio.h>  #define n   4  int main(void)  {     int a[n][n] =     {         { 1,  0,  0,  2 },              { 0,  3,  4,  0 },         { 0,  5,  6,  0 },         { 7,  0,  0,  8 }     };            ( size_t = 0; < n; i++ )     {          ( size_t j = 0; j < n; j++ ) printf( "%d ", a[i][j] );         printf( "\n" );     }      printf( "\n" );      ( int *first = ( int * )a, *last = ( int * )a + n * n;            first < last;            ++first, --last )     {         int tmp = first[0];         first[0] = last[-1];         last[-1] = tmp;     }      ( size_t = 0; < n; i++ )     {          ( size_t j = 0; j < n; j++ ) printf( "%d ", a[i][j] );         printf( "\n" );     }      printf( "\n" );      return 0; }