How to create Linked Array List in C#

Question

I need to create an Array with Linked list capacities.

Basically, I need a static index based list (like array), but with the possibility to get next and previous field (and easily loop back and forward through list, like with linked list). Note: Array is 2 dimensional. I use a custom class as array values. So I can set previous and next property for each instance.

Is there a built in C# collection for this? If not, any suggestions on how to create a very simple version of this? (I already have a version of this, consisting of 2 methods. One that loops forward to set the previous field, and one to loop backwards that set the next field, but it's still to messy).

Thanks in advance

EDIT:

The problem is my use of 2dimensional array. If loop through my array:

            for (byte x = 0; x < Grid.GetLength(0); x++) 
            {
                for (byte y = 0; y < Grid.GetLength(1); y++) /
                {
                    //At certain point, I need to get the previous field. I can do:
                    if (y != 0)
                    {
                        y -= 2; //-2 because I will y++ in for. Already getting messy
                    }
                    else 
                    {
//What if y == 0? Then I can't do y--. I should get max y and  do x-- to get previous element:

                        y = (byte)(Grid.GetLength(1) - 1); //to get max value y

                        x--;
                    }
}
    }

p.s.w.g · Accepted Answer · 2013-03-11 20:34:51Z

4

There is a built-in LinkedList<T> class.

But from your description why wouldn't an array work? It's static, and index-based, and you can easily get the next and previous element by incrementing / decrementing the index. It's hard to see exactly what you need from your code, but I'd like to point out that you can easily enumerate over a multi-dimensional array with:

var arry = new int[2,3];
foreach(var item in arry)
{
    ...
}

So you might be able to combine this with a Stack<T> structure (push items on the stack and pop them off to get the previous).

Alternatively, you can turn the array into a LinkedList directly.

var list = new LinkedList(arry.Cast<int>()); // flattens array

Or to preserve the indexes from the original array and still loop through the values as a linked list use:

var list = new LinkedList(arry.Cast<int>.Select((item, i) => new 
{ 
    Item = item, 
    Index1 = i % arry.GetLength(1), 
    Index2 = i / arry.GetLength(0) 
}));
var node = list.First;
while(node.Next != null)
{
    Console.WriteLine("Value @ {1}, {2}: {0}", node.Value.Item, node.Value.Index1, node.Value.Index2);
    // on some condition move to previous node
    if (...)
    {
        node = node.Previous;
    }
    else
    {
        node = node.Next;
    }
}

edited Mar 11, 2013 at 20:34

answered Mar 11, 2013 at 19:49

p.s.w.g

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3 Comments

dylanmensaert Over a year ago

Because I'm using a 2dimensional array. I will place code snippets and explain the problem in my answer rather then here. Ty :)

dylanmensaert Over a year ago

Thanks. It looks like I'm very bad at explaining :( As explained in the code (or at least tryed), I need to loop back and forward dynamically through the list, which I'm not able to do eassily (see comments in code) with a 2D array

p.s.w.g Over a year ago

@user1933169 Okay, I've updated my answer. I think I've provided a solution that suits your needs.

T.W.R. Cole · Accepted Answer · 2013-03-11 20:17:26Z

2

No, you don't. Instead of abandoning traditional arrays in lieu of "smart linked node arrays" which is what it seems like you're heading towards, try just adding a couple variables in your loop body:

byte x_len = Grid.GetLength(0);
byte y_len = Grid.GetLength(1);
byte prev_x, next_x, prev_y, next_y;

for (byte x = 0; x < x_len; ++x) 
{
  prev_x = x == 0? x_len - 1 : x - 1;
  next_x = x == x_len - 1? 0 : x + 1;
  for (byte y = 0; y < y_len; ++y)
  {
    prev_y = y == 0? y_len - 1 : y - 1;
    next_y = y == y_len - 1? 0 : y + 1;

    // here, you have access to the next and previous
    // in both directions, satisfying your requirements
    // without confusing your loop variables.

  }
}

answered Mar 11, 2013 at 20:17

T.W.R. Cole

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3 Comments

dylanmensaert Over a year ago

This is probably a good answer. But I'm far from familiar with the syntax your using.

p.s.w.g Over a year ago

@user1933169 ?: is the conditional or ternary operator.

dylanmensaert Over a year ago

k, will look into it. Tyvm

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