Retrieve values from next and previous elements in Sorted List C#

Question

I have a sorted list that will pass in two elements and compare the two. Is there a function in the SortedList class in C# that will do a next and previous? I got some help with a .Skip, but since the keys would be variable, how would that work? All I need to do is take in the first element and second element, then skip to the third and fourth, fifth and sixth, etc. I wish it were as simple as LinkedList's ".next.next."

  double velocity = positionList.Values.Skip(1);

Edit: The positionList is type

   <double, HandCoordinate>
   HandCoordinate = {double, double, double}

Does that help?

Thanks!

Answer 1

  List<int> ints = new List<int>();
  ints.Add(1);
  ints.Add(2);
  ints.Add(3);
  ints.Add(4);
  for (int i = 0; i < ints.Count; i += 2)
  {
    var pair = ints.Skip(i).Take(2);
    var first = pair.First();
    var last = pair.Last();
  }

Note: This should work, irrelevant of the type in theory. Unless the type is a drastically different format.

Without Skip() .

var pair = new { First = ints[i], Second = ints[i += 1] };

Answer 2

The question is somewhat unclear. I'm assuming you need to get pairs of things from a list?

It's fairly easy to write an extension method that will present a sequence of pairs of items from an IEnumerable:

using System;
using System.Collections.Generic;

namespace Demo
{
    internal static class Program
    {
        public static void Main()
        {
            double[] test = new double[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

            foreach (var pair in test.AsPairs()) // This is how you use it.
            {
                Console.WriteLine("({0}, {1})", pair.Item1, pair.Item2);
                // Or simply: Console.WriteLine(pair);
            }
        }
    }

    public static class EnumerableExt
    {
        public static IEnumerable<Tuple<T, T>> AsPairs<T>(this IEnumerable<T> sequence)
        {
            bool isFirst = true;
            T first = default(T);

            foreach (var item in sequence)
            {
                if (isFirst)
                {
                    first = item;
                    isFirst = false;
                }
                else
                {
                    isFirst = true;
                    yield return new Tuple<T, T>(first, item);
                }
            }
        }
    }
}

Answer 3

The class SortedList inherites IEnumerator , so you can use it:

SortedList list = ...
var listEnumerator = ((IEnumerable)list).GetEnumerator();
Pair<MyType> pair = null
do
{
    pair = Pair.Next<MyType>(listEnumerator);
    ...
}
while(pair != null)

...

class Pair<T>
{
    public T First {get; set;}
    public T Second {get; set;}

    public static Pair<T> Next<T>(IEnumerator enumerator)
    {
        var first = enumerator.Current;
        if(enumerator.MoveNext())
        {
           return new Pair<T>
               {
                   First = (T)first,
                   Second = (T)enumerator.Current,
               }
        }
        return null;
    }
}