[jira] [Commented] (COLLECTIONS-672) There are no List collection with optimized indexOf method.

["Gary Gregory (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COLLECTIONS-672?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16879383#comment-16879383 ] 

Gary Gregory commented on COLLECTIONS-672:
------------------------------------------

[~masyamandev]

It is best to provide a PR on GitHub to _this_ component.

> There are no List collection with optimized indexOf method.
> -----------------------------------------------------------
>
>                 Key: COLLECTIONS-672
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-672
>             Project: Commons Collections
>          Issue Type: Improvement
>          Components: Collection
>            Reporter: Aleksandr Maksymenko
>            Priority: Major
>
> All known implementations of List are all have O( n ) for indexOf() operation.
> Here is my implementation of such List on github which has O(log n) for indexOf() and contains():
>  [https://github.com/masyamandev/indexable-set]
> There are two modifications: one implements both List and Set, so it can contains unique elements, second modification can contains any amount of unique objects, but it's a bit slower.
> It's based on TreeList and provide complexity:
>  * get by index is O(log n)
>  * insertion, removing (both by index or by value) are O((log n) * (1 + log m)) where is amount of elements equals to inserted/removed element.
>  * insertion, removing are O(log n) if all elements are unique.
>  * indexOf and lastIndexOf are O(log n).
>  * contains is O(1) or (log n) depending on Map implementation.
> As those collections have complexity similar to TreeSet (at least in cases of unique elements), overall performance is 20-30% slower due to element indexing and eliminating some optimizations. However it provides fast indexOf and contains.
> Can I help in porting my code to Apache common Collections library?



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