程序代码：

#include<iostream>
#include<ctime>
using namespace std;

int main(int argc,char *argv[])
{
    srand((unsigned)time(NULL));
    int a,b,c;
    a=rand()%4;
    while((b=rand()%4)!=a)
        break;
    while((c=rand()%4)!=a && c!=b)
        break;
    printf("%d,%d,%d\n",a,b,c);
    return 0;
}