creating an array of arrays or 2D array dynamically

int ** arr = malloc(N*sizeof(int *));
for(i=0; i< N; i++) arr[i] = malloc(M*sizeof(int));

/* or you can use this simpler version*/
int (*arr)[M] = malloc(sizeof(int[N][M]));
/*  arr is pointer to int[M]
	use like arr[0][M-1];
	and free(arr); 
*/