#include <stdio.h>


    void Ex(void *_ret, int ret_len, int choice){
        if(choice==1){
            int *ret = _ret;              
            int i;
            for(i=0; i<ret_len; i++){
                ret[i] = i;
            }
         } else {
            int (*ret)[ret_len] = _ret;            
            int i, j;
            for(i=0; i<ret_len; i++){
                for(j=0; j<ret_len; j++){
                    ret[i][j] = i*j;
                }
            }
         }
    }

    int main(void) {
        int first[10];
        Ex(first, 10, 1);
        int second[20][20];
        Ex(second, 20, 2);
        
        printf("first[4] = %d\n", first[4]);
		printf("second[3][4] = %d\n", second[3][4]);

    }