Re: why 31 in hashcode for string

From:

Tom Anderson <twic@urchin.earth.li>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 12 Jun 2008 20:37:44 +0100

Message-ID:

<Pine.LNX.4.64.0806122036290.17211@urchin.earth.li>

On Thu, 12 Jun 2008, Andy Dingley wrote:

On 11 Jun, 15:46, Roedy Green <see_webs...@mindprod.com.invalid>
wrote:

The prime hint makes it trivial.

How would you go about writing a computer program to solves such
problems? People have no problem seeing new patterns.

In general, the same way Victorians evaluated polynomials with their
steam computers - the method of successive differences.

'The Victorian', surely - was there anyone other than Charlie the Cabbage?

Calculate the differences between successive terms of a series, then the
differences between successive differences, and pretty soon a "subtle"
pattern will throw up an "obvious" pattern in its diffs.

Of course this fails dismally for primes! In that case, you'd compare
the differences to a set of "well known sequences", primes being an
obvious candidate, along with the birthdates of US Presidents, run
lengths of Startrek movies, etc. according to the relevant fandom of the
cryptographer setting the puzzle.

For the lazy and/or smart, searchy searchy:

http://www.research.att.com/~njas/sequences/

tom

--
We do what we must because we can.