2016a_87que2

 public static int passingCars(int[] a)
    {
        int count = 0;
        int howManyEastTillNow = 0;
        for(int i = 0; i < a.length; i++)
            if(a[i] == 0)
                howManyEastTillNow++;
            else//a[i] = 1
                count += howManyEastTillNow;
        return count;
    }