C＃-如何重新排列新的HashSet <int> 从最小到最大

Question

I'll apologize upfront but I'm not sure of how to exactly word this question.

I have a piece of code that works fine currently that it's sole purpose is to find all the combinations of unique identifiers. And that works fine, but what I'm trying to do is create an iteration that will truly make the combinations unique.

What I mean is below, you'll see a simple piece of code. that adds to HashSet to a list. And then you'll see a method which created a new Hashset list. I know if I can order whats in each HashSet then it will make itself unique.

static void Main(string[] args)
    {

        List<HashSet<int>> myInts = new List<HashSet<int>>();
        myInts.Add(new HashSet<int>{1, 2});
        myInts.Add(new HashSet<int>{2, 1});
    }

   private static List<HashSet<int>> RemoveDuplicates(List<HashSet<int>> hash)
    {
        List<HashSet<int>> returnSet = new List<HashSet<int>>();
        for (int i = 0; i < hash.Count; i++)
        {
           //do the order here and add it to the return set

        }


        return returnSet;

    }

So the code is correct, 1,2 is different from 2,1 however, in my objects they are the same combination. So my though process is if I could order the array then the HashSet will make it unique because both will be 1,2

Answer 1

You don't need to order items, you can use SetEquals to check if the sets contain the same elements.

private static List<HashSet<int>> RemoveDuplicates(List<HashSet<int>> hash)
{
    List<HashSet<int>> returnSet = new List<HashSet<int>>();
    for (int i = 0; i < hash.Count; i++)
    {
        var isDupe = false;
        //do the order here and add it to the return set
        for (int j = i + 1; j < hash.Count; j++)
        {
            if(hash[i].SetEquals(hash[j]))
            {
                isDupe = true;
                break;
            }
        }
        if (!isDupe)
        {
            returnSet.Add(hash[i]);
        }
    }
    return returnSet;
}

This is quite expensive though, assuming SetEquals is O(n) and you have k sets, that will be O(n*k ² )