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 use a HashSet. HashSet is a collection used for guarantee uniqueness and you can compare items on collection, Intersect, Union. etc.

Pros: No duplicates, easy to manipulate groups of data, more efficient Cons: You can't get a specific item in the collection, for example: list[0] doesn't work for HashSets. You can only Enumerating the items. e.g. foreach

Here is an example:

using System;
using System.Collections.Generic;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            HashSet> intArrList = new HashSet>(new HashSetIntComparer());
            intArrList.Add(new HashSet(3) { 0, 0, 0 });
            intArrList.Add(new HashSet(5) { 20, 30, 10, 4, 6 });  //this
            intArrList.Add(new HashSet(3) { 1, 2, 5 });
            intArrList.Add(new HashSet(5) { 20, 30, 10, 4, 6 });  //this
            intArrList.Add(new HashSet(3) { 12, 22, 54 });
            intArrList.Add(new HashSet(5) { 1, 2, 6, 7, 8 });
            intArrList.Add(new HashSet(4) { 0, 0, 0, 0 });

            // Checking the output
            foreach (var item in intArrList)
            {
                foreach (var subHasSet in item)
                {
                    Console.Write("{0} ", subHasSet);
                }

                Console.WriteLine();
            }            

            Console.Read();
        }

        private class HashSetIntComparer : IEqualityComparer>
        {
            public bool Equals(HashSet x, HashSet y)
            {
                // SetEquals does't set anything. It's a method for compare the contents of the HashSet. 
                // Such a poor name from .Net
                return x.SetEquals(y);
            }

            public int GetHashCode(HashSet obj)
            {
                //TODO: implemente a better HashCode
                return base.GetHashCode();
            }
        }
    }
}


Output:
0
20 30 10 4 6
1 2 5
12 22 54
1 2 6 7 8

Note: Since 0 is repeated several times, HashSet considers the 0 only once. If you need diferentiate between 0 0 0 0 and 0 0 0 then you can replace HashSet> for HashSet> and implement a Comparer to the List instead.

You can use this link to learn how to compare a list: https://social.msdn.microsoft.com/Forums/en-US/2ff3016c-bd61-4fec-8f8c-7b6c070123fa/c-compare-two-lists-of-objects?forum=csharplanguage

If you want to learn more about Collections and DataTypes this course is a perfect place to learn it: https://app.pluralsight.com/player?course=csharp-collections&author=simon-robinson&name=csharp-collections-fundamentals-m9-sets&clip=1&mode=live