Data/File Structure and Algorithm for Retrieving Sorted Data Chunk Efficiently

Jane Austine janeaustine50 at hotmail.com
Tue Oct 5 12:12:24 CEST 2004


Hello.

I have student_names and their scores, which are between 0..100.

I want to retrieve in the sorted order in terms of score, Nth
student's name to N+10th student's name along with their scores.
(suppose a web page showing top 10 students and there are "next page"
link and if you follow the link there shows next top 10 students with
"prev" and "next" page links.)

The list is dynamically resized -- elements are added or deleted. The
list could go fairly long enough that pulling all the data on memory
at once is not a good choice.

What algorithm and data/file structure are most efficient? (the
environment is "cgi" based web environment)

Simplest approach would be using btree from bsddb. But there are only
"first"/"last" and "next"/"prev" moves. If I have to retrieve 20..29th
students, I have got to "first" and then "next" 19 times before I
finally get to 20th student, which is a waste of time(and memory).
Maybe I could keep the cursor position among sessions if I were using
a standalone server. However, it is in CGI environment.

What can I do instead? What data structure allows you to access
nth..n+10th data from the sorted list in a constant time?

Jane



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