Delete duplicates in a List of int arrays

Question

having a List of int arrays like:

List intArrList = new List();
intArrList.Add(new int[3] { 0, 0, 0 });
intArrList.Add(new int[5] {         


        

Answer 1

You can define your own implementation of IEqualityComparer and use it together with IEnumerable.Distinct:

class MyComparer : IEqualityComparer 
{
    public int GetHashCode(int[] instance) { return 0; } // TODO: better HashCode for arrays
    public bool Equals(int[] instance, int[] other)
    {
        if (other == null || instance == null || instance.Length != other.Length) return false;

        return instance.SequenceEqual(other);
    }
}

Now write this to get only distinct values for your list:

var result = intArrList.Distinct(new MyComparer());

However if you want different permutations also you should implement your comparer this way:

public bool Equals(int[] instance, int[] other)
{
    if (ReferenceEquals(instance, other)) return true; // this will return true when both arrays are NULL
    if (other == null || instance == null) return false;
    return instance.All(x => other.Contains(x)) && other.All(x => instance.Contains(x));
}

EDIT: For a better GetashCode-implementation you may have a look at this post as also suggested in @Mick´s answer.