#include <stdlib.h>
#include <stdio.h>
#include <time.h>

void swap(int *a, int *b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}

void genarate(int arr[])
{
    int range = 10;
    int i;

    for(i = 0; i < 10; ++i)
        arr[i] = i;

    while(range)
    {
        i = rand() % range;
        --range;
        swap(&arr[i], &arr[range]);
    }
}

void pick_four(int arr[], int result[])
{
    int i;
    int n;
    if(arr[0] == 0)
    {
        n = (rand() % 9) + 1;
        swap(&arr[0], &arr[n]);

        for(i = 0; i < 4; ++i)
            result[i] = arr[i];

        swap(&arr[0], &arr[n]);
    }
    else
    {
        for(i = 0; i < 4; ++i)
            result[i] = arr[i];
    }
}

int main(void)
{
    int arr[10];
    int result[4];
    int i;


    srand((unsigned int)time(NULL));

    genarate(arr);

    pick_four(arr, result);

    for(i = 0; i < 4; ++i)
        printf("%d", result[i]);
    printf("\n");

    return 0;
}