Re: "PriorityMap"

From:
Patricia Shanahan <pats@acm.org>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 30 Mar 2008 14:13:48 -0700
Message-ID:
<13v00ke2klg08ee@corp.supernews.com>
Andreas Leitgeb wrote:

I'm in search of a data structure for the followig usecase:

Some algorithm spits out *lots* of pairs (k,v) of type (int,long).
I only want either those ten(*) pairs with the lowest keys, or all
pairs with the lowest ten(*) keys. (whichever is easier to achieve)
The keys (k) are not necessarily unique, in fact I usually get a
couple of different values (v) for each k, and I'm interested only
in the v's, that came with those ten(*) smallest k's. The actual
k's do not matter afterwards.

There are much too many to save them all and filter afterwards.

PriorityQueue and TreeMap do not seem to make it easy to
efficiently prune them beyond the first ten(*) entries
after each add().


I'd use a PriorityQueue but with either a Comparable element type or a
Comparator that uses descending order of the key values. That way, the
head item is the one with the largest key, and the one that should be
removed when an insertion increases the queue size beyond 10.

Patricia

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