How to find the opposite variables list?

Questions & Answers
1

OK, I want to know how would be a script describing the opposite variables list like this example:

list_nums[0]=1;
list_nums[1]=2;
list_nums[2]=3;
list_nums[3]=4;
list_nums[4]=5;
useful_var[0] = 3;
useful_var[1] = 4;

and with this information that says the list of numbers is the number 5 and the useful variable are 3 and 4 I want to be able to know the opposite of the useful variable. In this case it would end something like this.

notuseful[0] = 1;
notuseful[1] = 2;
notuseful[2] = 5;

So what I want to know is how can I find the opposite of this variables.

Note: I am trying to do this to have like it says 1 and 2 so if you press 1 and 2 is correct but if you press 1,2 and 3 is wrong.

Thanks... for future :P

2

I'd use C# generic Lists ...

using System.Collections.Generic;

...

List<int> list_nums = new List<int>();
list_nums.Add(1);
list_nums.Add(2);
list_nums.Add(3);
list_nums.Add(4);
list_nums.Add(5);

List<int> useful_var = new List<int>();
useful_var.Add(3);
useful_var.Add(4);

List<int> notuseful = new List<int>();
foreach (int num in list_nums)
{
    if (!useful_var.Contains(num))
    {
        notuseful.Add(num);
    }
}