[jira] [Commented] (COLLECTIONS-479) An Order Statistic Tree

["Thomas Neidhart (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COLLECTIONS-479?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14577892#comment-14577892 ] 

Thomas Neidhart commented on COLLECTIONS-479:
---------------------------------------------

Looking through some old issue, COLLECTIONS-181 talks about the same problem but proposes another solution.

>From the referenced issue, I like the proposed interface: IndexedSortedMap.

In total there are 4 approaches proposed:

 * create a concrete class with a sorted array as backing data structure
 * create a decorator with a sorted list as backing data structure
 * create a concrete class with a counted red-black tree
 * create a concrete class with an counted AVL tree

> An Order Statistic Tree
> -----------------------
>
>                 Key: COLLECTIONS-479
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-479
>             Project: Commons Collections
>          Issue Type: New Feature
>            Reporter: Ajo Fod
>            Priority: Minor
>             Fix For: 4.x
>
>         Attachments: COLLECTIONS-479.patch, NodeExistsException.java, RedBlackBST.java
>
>
> An order statistic tree http://en.wikipedia.org/wiki/Order_statistic_tree provides two useful properties. The ability to rank arbitrary keys relative to keys existing in the tree AND the ability to retrieve elements from the tree with the given rank.
> This can be used to find the percentile rank of a key for example.
> This functionality is not yet provided yet by any of the major libraries AFAIK.



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