Using non repeating random number (in C)

I have been given the assignment to create a non-repeating number generator, which generates 7 numbers. I have used the rand function. But not sure how to make sure the numbers are not repetitive. Thanks for the help

    int i, n;
    time_t t;
    n = 7;
    srand((unsigned) time(&t));

    for( i = 0 ; i < n ; i++ ) {
    printf("%d\t", rand() % 35);}