From: Mason Kelsey <masonkelsey@...>
Date: 2009-09-21T11:25:17+09:00
Subject: Multi-Dimensional Arrays in Priority Queues

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In my program I need to construct a priority queue that sorts ascending.
The basic idea can be expressed in the following simple code that uses a
Priority Queue concept.  See:
http://www.math.kobe-u.ac.jp/~kodama/tips-ruby-pqueue.html

1   require "pqueue"
2
3   pq=PQueue.new(proc{|x,y| x<y})
4   pq.push(2)
5   pq.push(3)
6   pq.push(4)
7   pq.push(3)
8   pq.push(2)
9   pq.push(4)
10 print "size:"+pq.size.to_s+"\n"
11 print "each_pop: "
12 pq.each_pop{|x| print x.to_s+" "}
13 print "\n"

This is clean and simple to understand.  But I need to be able to put into
the queue several components per push to make an entire record object.  I
need to have three components: an integer heuristic value, followed by two 9
digit configuration patterns, such as
pq.push([2], [123456780], [123456708])  But this gives me an argument error
message:
pqueue.rb:4:in `push': wrong number of arguments (3 for 1)
(ArgumentError) from pqueue.rb:4

or pq.push(2_123456780_123456708) ignores the underscore separators and runs
the 3 parts together as one long number.

Still learning Ruby and none of the books address multiple dimensional
arrays very well.  Is the Priority Queue not able to handle
multi-dimensional arrays?  Can this code be modified to allow multi-elements
in each push and still sort on the first element?

If I cannot use pqueue, is there another required library of methods that
will work with three elements in each array entry?

Thanks in advance to those of you who can help.  And thanks to all who help
out on this forum.  Very good forum.

No Sam

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