Get unique digits from array

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

int main()
{
    int a[]= {2,8,121,42,222,23};
    int b[100] = {}; ///array to store unique digits and check them with tmp
    int unique_digit_products = 0;
    int len;
    int len_b = 1; ///length of array with unique digits
    int i,j;
    int tmp;
    int multiplication = 1;
    int reminder;
    int unique_digits = 0;

    ///set len to length of array (count from 0)
    len = 6;

    for(i=0; i < len; i++)
    {
        tmp = a[i]; ///get value of array at i index
        while(tmp !=0)
        {
            reminder = tmp % 10;
            multiplication *= reminder;
            tmp /= 10;
        }

        for(j=0; j < len_b; j++)
        {
            if(multiplication == b[j])
            {
                break;
            }
            else
            {
                if(j == len_b-1)
                {
                    b[len_b-1] = multiplication;
                    len_b++;
                    unique_digits++;
                    break;
                }
            }
        }
        multiplication = 1;
    }

    printf("unique digits: %d\n",unique_digits);
    printf("uniqe digits are: ");
    for(i=0; i < unique_digits; i++)
    {
        printf("%d ",b[i]);
    }
    return 0;
}