Subj : Re: Order-preserving hash of strings
To   : comp.programming
From : William
Date : Fri Sep 16 2005 02:41 pm

"Alex Fraser" <me@privacy.net> wrote in message
news:_cCdnTe9YZC-FbfenZ2dnUVZ8qCdnZ2d@eclipse.net.uk...
> "Digital Puer" <digital_puer@hotmail.com> wrote in message
> news:1126832235.004650.149620@g43g2000cwa.googlegroups.com...
> > Hi, suppose I have a list of character strings and want
> > to hash them to integers for use in a lookup table. The
> > problem is that the hashed values need to preserve the
> > order that the strings occurred in the list. For example,
> > a possible hashing of a list of three strings would be
> > is 9, 12, 30 respectively; an illegal hashing would be
> > 7, 5, 2 (this hashing does not preserve the order).
>
> This sounds tricky at best, if the list of strings is known in advance and
> fixed, and probably totally impractical otherwise.
>
> Would an array (or list) of the strings in order, and a hash table
> containing array indexes (or pointers to list items) solve the problem?

That's how I did it. I needed to parse ordered properties
files and rewrite them (using Java) so I rolled my own
properties class that provided an ordered array and a hash
of indices. Simple and fun. -Wm

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