将M*N的矩阵旋转90度

#include   
using namespace std;  
const int M = 5;  
const int N = 3;  
  
int main()  
{  
  int a[M][N] = {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};  
  int *p = a[0];  
  
  for(int i = 0;i < M;i++) // M = 5   
  {  
    for(int j = N-1;j >= 0;j--) // N = 3  
    {  
        cout << *(p + i + j*M) << ","; // M = 5;  
    }  
    cout << endl;  
  }    
  return 0;  
}