按升序和降序对链接列表进行排序

Question

I have a generic linked list, currently made up of ints, and I want to sort them by ascending order by default, and then switch a boolean to sort them by descending values. How would I go about doing this?

Answer 1

Assuming your linked list implements IEnumerable<T> (which it probably should!), you can just use the LINQ functions OrderBy and OrderByDescending .

For ints, the default comparer is fine, so you would just write:

bool ascending = true;
var orderedEnumerable = ascending ? collection.OrderBy(x => x) : collection.OrderByDescending(x => x);

Or, with a function and default args:

IOrderedEnumerable<int> GetOrderedNumbers(bool ascending = true)
{
      return ascending ? collection.OrderBy(x => x) : collection.OrderByDescending(x => x);
}

MSDN for OrderBy: http://msdn.microsoft.com/en-us/library/vstudio/bb534966(v=vs.100).aspx

Answer 2

If you use the .NET's LinkedList<T> that, in its turn, implements IEnumerable<T> you can use some of these solutions:

This extension method returns a sorted copy of type LinkedList<T>

public static LinkedList<TSource> SortedAscending<TSource, TKey>(
    this LinkedList<TSource> source,
    Func<TSource, TKey> keySelector)
{
    LinkedList<TSource> tempLinkedList = new LinkedList<TSource>();
    IEnumerable<TSource> orderedEnumerable = source.OrderBy(keySelector).AsEnumerable();
    orderedEnumerable.ForEach(value => tempLinkedList.AddLast(value));
    return tempLinkedList;
}

This extension method sorts the source of type LinkedList<T>

public static void SelfSortAscending<TSource, TKey>(
    this LinkedList<TSource> source,
    Func<TSource, TKey> keySelector)
{
    LinkedList<TSource> tempLinkedList = new LinkedList<TSource>(source);
    source.Clear();
    IEnumerable<TSource> orderedEnumerable = tempLinkedList.OrderBy(keySelector).AsEnumerable();
    orderedEnumerable.ForEach(value => source.AddLast(value));
}

Extension methods for descending ordering you can find at: LinkedListHelper (GitHub link)

By the way, .ForEach() you could implement like this:

public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
{
    if (action == null)
        throw new ArgumentNullException(nameof(action));

    foreach (T element in source)
        action(element);
}