Appropriate list-like sorted data structure

Question

I am looking for a list-like data structure with the following properties:

Generic, i.e., DataStructure<T>, where T is generic
Multiple different instances of T which are considered equal by IComparable<T> must be allowed to be present in the list at the same time; their order can be arbitrary (even change), but they must come after "smaller" instances of T and before "larger" instances of T
O(log(n)) insertion time complexity (or faster)
O(log(n)) retrieval time complexity (or faster)
Possibility to access the first/last element with O(1) time complexity
Possibility to access the predecessor/successor of an element with O(1) time complexity
Available without the use of additional libraries

I do not care about removal time complexity since elements only need to be deleted very rarely. I also do not care about space complexity.

I know that there is no data structure which fulfills all properties, but the ones from the BCL (which look like they could do what I need at first glace) seem to have too many disadvantages:

SortedSet<T> does not allow multiple instances which are considered the same by IComparable<T> (2) and does not have predecessor/successor functions (6)
SortedSet<T, List<T>> (with only one "representative" indexing instance of T) would require quite some additional (ugly) code, and there is still no predecessor/successor function (6)
SortedList<T, T> is too slow for insertion (3)
SortedDictionary<T, T> does not allow multiple instances which are considered the same by IComparable<T> (2) and does not allow accessing the first/last element directly (5), nor does it have predecessor/successor functions (6)
Inheriting from List<T> and keeping it sorted would possibly be an option, but I'd rather use something that is built-in (7) due to the implementation effort and the potentially poor performance

Am I overlooking something? There seem to be no other relevant data structures for my use case (I looked here and here, among others). Is there another data structure which I did not consider?

Perhaps a skip list would be a good fit? I don't know of any "built-in" implementation, though; why don't you want to take on additional dependencies? — Cameron, Jun 15 '15 at 17:51
Why not just add the Hash to the IComparable on a SortedSet? — paparazzo, Jun 15 '15 at 18:18
@Blam: I tried that, but when calling `GetViewBetween` with two "identical" objects, I have a 50% chance of getting an exception thrown since `GetViewBetween` expects the smaller object first. Depending on their hash, this is only true half the time (statistically speaking). — Andreas Unterweger, Jun 15 '15 at 18:24
I am wondering if you could not get lower to return a hash of zero and higher to return a hash int32max — paparazzo, Jun 15 '15 at 19:17
@Blam: The probability should be zero, i.e., there should never be a case where an insertion fails. — Andreas Unterweger, Jun 16 '15 at 07:07
I was not saying anything about insert. I clearly have nothing of value to add. — paparazzo, Jun 16 '15 at 07:14
@Blam: Sorry, maybe I misunderstood your comment then. What were you suggesting? — Andreas Unterweger, Jun 16 '15 at 09:26

score 0 · Answer 1 · answered Dec 07 '15 at 04:40

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If you're willing to relax 5 and 6 then you might be able to use a TreeMap

answered Dec 07 '15 at 04:40

pgpb.padilla

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Thanks for pointing this out, but unfortunately I cannot relax those two requirements. – Andreas Unterweger Dec 07 '15 at 09:31

Appropriate list-like sorted data structure

1 Answers1