[Purdue-pm] fast table lookup of randomly associated items

Rick Westerman westerman at purdue.edu
Wed May 19 12:41:42 PDT 2010

----- Original Message -----
> Hash: SHA1
> Say I have a table like the following:
> number Item
> 1-5 A
> 6 B
> 7-12 C
> 13-20 D
> 21-25 E
> 26-30 F
> Say I then have a random number generator that spits out a number from
> 1-30.
> What is the fastest way to look up the item associated with that
> random number?

   Fastest?  I'd say a simple array lookup.  Could be quite memory intensive but, at least in 'C' and I presume Perl, array lookups are simple pointer additions.   Can't be any faster than that as long as you do not exceed physical memory boundries.

> For more fun, say I want to store that table in a text file what is a
> good way to represent that?

   I sort of liked your human readable format above.  JSON is fine but not as clear to the lay person.

   All-in-all could be a good challenge problem.
Rick Westerman 
westerman at purdue.edu

Bioinformatics specialist at the Genomics Facility.
Phone: (765) 494-0505           FAX: (765) 496-7255
Department of Horticulture and Landscape Architecture
625 Agriculture Mall Drive
West Lafayette, IN 47907-2010
Physically located in room S049, WSLR building

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