Distinct list of lists, where lists contains same values but in different order

Question

I got a list:

var list = new List>();

which could contain

list[0] = {1, 2, 3, 4}
lis         


        

Answer 1

You could write your own implementation of IEqualityComparer>. For GetHashCode() it would simply return the XOR of all the hash codes of the elements in the list. For Equals() it would create a new HashSet from the first list, and call HashSet.SetEquals on it, passing in the second list. This assumes there will be no duplicate elements, mind you. (Otherwise { 1, 1, 2 } will be equal to { 1, 2, 2 } but have a different hash code.)

Once you've got that far, you can use Distinct:

var distinct = list.Distinct(new CustomEqualityComparer());

As an alternative approach, could you use HashSet as your collection type to start with? Then it's really easy:

var distinct = sets.Distinct(HashSet.CreateSetComparer());

If you need lists as the input but can cope with sets as the output:

var distinct = list.Select(x => new HashSet(x))
                   .Distinct(HashSet.CreateSetComparer());