Program to rotate a 2-D square matrix by 90 degree

say you have a 4x4 two dimensional array, 

write a function that rotates it 90 degrees 

[1][2][3][4]
[5][6][7][8]
[9][0][1][2]
[3][4][5][6]

Becomes:

[3][9][5][1]
[4][0][6][2]
[5][1][7][3]
[6][2][8][4] 

This is working code in C, which accepts the size 

of square matrix and matrix elements and prints

the rotated matrix.

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

int main()
{
 int s, **arr, **arr2;
 int i, j, c, r;
 printf("\n Enter the size of square matrix : ");
 scanf("%d",&s);
 arr=(int *)malloc(s*sizeof(int));
 arr2=(int *)malloc(s*sizeof(int));
 printf("\n Enter the array elements :");
 for(i=0;i<s;i++)
 {
  arr[i]=(int *)malloc(s*sizeof(int));
  arr2[i]=(int *)malloc(s*sizeof(int));
 }
 for(i=0;i<s;i++)
  {
  printf("\n Enter the %d the row : ", i);
  for(j=0;j<s;j++)
   {
    c=s-1-i;
    r=j;
    scanf("%d",&arr[i][j]);
    arr2[r][c]=arr[i][j];
   }
 }

 for(i=0;i<s;i++)
 {
  printf("\n");
  for(j=0;j<s;j++)
  {
   printf("%d ", arr2[i][j]);
  }
 }
}