Algorithms for finding a numerical record in a list of ordered numbers

Posted by Ankur on Stack Overflow See other posts from Stack Overflow or by Ankur
Published on 2010-04-23T08:46:32Z Indexed on 2010/04/23 9:03 UTC
Read the original article Hit count: 433

Filed under:

database

|

indexing

|

algorithm

I have a list of incomplete ordered numbers. I want to find a particular number with as few steps as possible.

Are there any improvements on this algorithm, I assume you can count the set size without difficulty - it will be stored and updated every time a new item is added.

Your object is to get your cursor over the value x

The first number (smallest) is s, and the last number (greatest) is g.

Take the midpoint m1 of the set: calculate is x < m1,
If yes then s <= x < m1
If no then m1 < x <= g
If m1 = x then you're done.

Keep repeating till you find x. Basically dividing the set into two parts with each iteration till you hit x.

The purpose is to retrieve a numerical id from a very large table to then find the associated other records.

I would imagine this is the most trivial kind of indexing available, are there improvements?

© Stack Overflow or respective owner

Related posts about database

SQL SERVER Retrieve and Explore Database Backup without Restoring Database Idera virtual database

as seen on Dot net Slackers - Search for 'Dot net Slackers'
I recently downloaded Ideras SQL virtual database, and tested it. There are a few things about this tool which caught my attention.My ScenarioIt is quite common in real life that sometimes observing or retrieving older data is necessary; however, it had changed as time passed by. The full database… >>> More
Cloning A Database On The Same Server Using Rman Duplicate From Active Database

as seen on Oracle Blogs - Search for 'Oracle Blogs'
To clone a database using Rman we used to require an existing Rman backup, on 11g we can clone databases using the "from active" database option. In this case we do not require an existing backup, the active datafiles will be used as the source for the clone. In order to clone with the source database… >>> More
cPickle ImportError: No module named multiarray

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, I'm using cPickle to save my Database into file. The code looks like that: def Save_DataBase(): import cPickle from scipy import * from numpy import * a=Results.VersionName #filename='D:/results/'+a[a.find('/')+1:-a.find('/')-2]+Results.AssType[:3]+str(random.randint(0,100))+Results.Distribution+"… >>> More
SQL SERVER – 2008 – Introduction to Snapshot Database – Restore From Snapshot

as seen on SQL Authority - Search for 'SQL Authority'
Snapshot database is one of the most interesting concepts that I have used at some places recently. Here is a quick definition of the subject from Book On Line: A Database Snapshot is a read-only, static view of a database (the source database). Multiple snapshots can exist on a source database and… >>> More
OTN ???? ?????? ???????

as seen on Oracle Blogs - Search for 'Oracle Blogs'
Database ?? Database ??????? Database ?????????? Java WebLogic Server/????????·???? SOA/BPM/????? ???????/???? ID??/?????? ?????EPM/BI EPM/BI ??????? EPM/BI ???? OS/??? ???? ????? MySQL Database ?? ???? ?? ????????? ??? ?? ORACLE MASTER… >>> More

Related posts about indexing

IIS6 Indexing Service indexing asp.net codebehind (.aspx.cs) files

as seen on Server Fault - Search for 'Server Fault'
I've setup a few catalogs on an Windows Server 2003 IIS6 install, each tracking files within a website. In the Properties - Generation Dialog for each catalog, 'Index files with unknown extensions' is turned OFF. 'Inherit above settings from Service' in that dialog is also turned off. However, the… >>> More
Outlook 2007 OST File Indexing and OneNote 2007 Indexing are Broken

as seen on Super User - Search for 'Super User'
I'm running Outlook 2007 under Windows 7 Home Premium RTM. My OST file was previously being properly indexed but eventually searches significantly slowed down so I suspected a problem. Searching and indexing appears broken in OneNote 2007 as well as search time is now significantly longer. I brought… >>> More
Indexing vs. no indexing when inserting records

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a few questions about whether or not it would be best to not use indexing. BACKGROUND: My records have a timestamp attribute, and the records will be inserted in order of their timestamps (i.e., inserted chronologically). QUESTIONS: If I DON'T use indexing is it typical for the database… >>> More
SQL SERVER – Transcript of Learning SQL Server Performance: Indexing Basics – Interview of Vinod Kumar by Pinal Dave

as seen on SQL Authority - Search for 'SQL Authority'
Recently I just wrote a blog post on about Learning SQL Server Performance: Indexing Basics and I received lots of request that if we can share some insight into the course. Here is 200 seconds interview of Vinod Kumar I took right after completing the course. We have few free codes to watch the course… >>> More
Can the Windows Indexing Service restart an app pool if it doesn't index the Web.Config?

as seen on Stack Overflow - Search for 'Stack Overflow'
I am having a slight debate with a colleague of mine on this subject. Scenario: A web site has a sub directory that is indexed using the Windows Indexing Service. There is not a web.config in this directory and the indexing service is not indexing the parent directory which is the site root. Something… >>> More