Question

I have a SortedDictionary as defined like this:

SortedDictionary<TPriority, Queue<TValue>> dict;

But I want to maintain the dict in reverse order. I assume I need set the Comparer, but what comparer do I use for a generic TPriority? Note that TPriority implements IComparable.

Answer 1

You can create a reverse comparer quite easily:

public sealed class ReverseComparer<T> : IComparer<T> {
    private readonly IComparer<T> inner;
    public ReverseComparer() : this(null) { }
    public ReverseComparer(IComparer<T> inner) {
        this.inner = inner ?? Comparer<T>.Default;
    }
    int IComparer<T>.Compare(T x, T y) { return inner.Compare(y, x); }
}

Now pass that into the constructor for the dictionary:

var dict = new SortedDictionary<TPriority, Queue<TValue>>(
                 new ReverseComparer<TPriority>());