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From: alain@cs.uchicago.edu (Alain Roy)
Subject: Re: "AI Complete" vs the Root Analysis
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References: <41d64d$ped@Mars.mcs.com> <MIKEW.95Aug22151617@hobbes.cs.washington.edu> <DDrDuz.8zt@aisb.ed.ac.uk>
Date: Wed, 23 Aug 1995 14:08:47 GMT
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In article <DDrDuz.8zt@aisb.ed.ac.uk>, andrewt@aisb.ed.ac.uk (Andrew
Tuson) wrote:

>I hate to admit that I`m unsure of the difference between NP-complete and
>NP-hard myself...:-(
>
>Maybe someone should post a clear explanation...(I`ve looked through
>the FAQ but couldn`t find anything suitable)...

NP-Hard means that a problem is at least as hard as any problem in NP. 
A problem is NP-Complete if it's NP-Hard and in NP.

Good discussions of NP-Completeness are in many textbooks. One good book
is "Algorithms" by Cormen, Leiserson, and Rivest (Chapter 36). Don't buy
it just for the NP-Completeness-it's only one chapter out of 37. But it's
a common book that you're likely to find in a good library. (Incidentally,
it's an excellent book for learning about various algorithms.)

-alain
