Question

I have a linked list constructed as follows:

LinkedList<int> linked = new LinkedList<int>();
var array = new int[] { 23, 55, 64, 65 };
foreach (var item in array)
{
    linked.AddLast(item);
}

How do I find the index of the number 64?

Answer 1

The only way is to check element by element and increase a counter (by “only way”, I am saying that other methods like LINQ need to do the same thing internally).

A hand-written extension method would look something like this:

public static class LinkedListExt
{
    public static int IndexOf<T>(this LinkedList<T> list, T item)
    {
        var count = 0;
        for (var node = list.First; node != null; node = node.Next, count++)
        {
            if (item.Equals(node.Value))
                return count;
        }
        return -1;
    }
}

But it can easily be done using LINQ as @L.B wrote (yielding the same time complexity).