How to escape from duplicates values in List of Lists c#

Question

var _array = new int[] { -4, -2, -1, 1, 2, 4 };

var keepPerms = new List<List<int>>();

        var _l = new List<int>();
        var c = 0;
        while (c != 2)
        {
            for (int i = 0;i < _array.Length; i++)
            {
                _l.Add(_array[i]);
                List<int> _sort = _l.OrderBy(s => s).ToList();
                if (!keepPerms.Contains(_sort))
                    keepPerms.Add(_sort);
                

            }
            _l.Clear();
            
            c++;
        }
        foreach (var item in keepPerms)
        {                
            {
                Console.WriteLine(String.Join(" ", item));
            }
            Console.WriteLine();
        }
        Console.WriteLine();

Output i get:

-4

-4 -2

-4 -2 -1

-4 -2 -1 1

-4 -2 -1 1 2

-4 -2 -1 1 2 4

-4

-4 -2

-4 -2 -1

-4 -2 -1 1

-4 -2 -1 1 2

-4 -2 -1 1 2 4

Output i need:

-4

-4 -2

-4 -2 -1

-4 -2 -1 1

-4 -2 -1 1 2

-4 -2 -1 1 2 4

It's a prototype of method where i need to find subsets of some sequnce. The main problem is that after doing this method i get duplicates of subsets. Is there any way to get the original values of list, despite the number of times I called it? Can you advise better way to find thise originals values of list.

What is this "output", I see no `Console.Write` line or similar. Also, could you perhaps make clear what the expected output would be? — Klaus Gütter, Feb 26 '22 at 11:24
Does this answer your question? [Remove duplicates from a List in C#](https://stackoverflow.com/questions/47752/remove-duplicates-from-a-listt-in-c-sharp) — gokhancevik, Feb 26 '22 at 15:45
@gokhancevik i didn't clearly understand how does the HashSet work. — Gienko, Feb 26 '22 at 17:18

score 0 · Answer 1 · answered Feb 26 '22 at 11:45

0

You get two results because of the condition while(c != 2), you can switch it to while(c != 1) and will work or you can just remove the while as is not really helpful in your case.

answered Feb 26 '22 at 11:45

tlucian

161
1
6

score 0 · Accepted Answer · answered Feb 26 '22 at 14:26

List.Contains() use default equality comparer. List<int> a == List<int> b only if it's same objects. You should use custom equality comparer in Contains() or use Any + SequenceEqual:

if (!keepPerms.Any(item => item.SequenceEqual(_sort)))
  keepPerms.Add(_sort);

How to escape from duplicates values in List of Lists c#

2 Answers2