Subj : Re: Sorting
To   : borland.public.cpp.borlandcpp
From : Nokomis <nokomis@radiolink.net>
Date : Wed Dec 17 2003 07:38 pm



Bob Gonder wrote:

> Nokomis wrote:
>
> >Anyone know an algorithm for sorting large numbers of character strings?
> >
> >Something like a telephone direcctory - too big for a normal array.
>
> Data resides in a file?
> Is this fixed-length records or variable?
> You know Bubble Sort, right?
>
> Use Bubble Sort algorythm for the outside block, and the fastest sort
> you care to use for the inner block.
>
> Array[2000]
> RecordPointer   A=0,B;
>
> while( A < FileRecords-1000 )
> {
>         read 1000 records from A into Array[0]
>         B = A+1000
>         if( B >= FileRecords )
>                 fastsort 2000 records   /* small file */
>         while( B < FileRecords )
>         {       read 1000 records from B into Array[1000]
>                 fastsort 2000 records
>                 write 1000 records to B from Array[1000]
>                 B+=1000
>         }
>         write 1000 records to A from Array[0]
>         A += 1000
> }
> Adjust "1000" to suit your memory/speed requirements.
> Since this is an "in-place" sort, it would be safer to copy the file,
> sort the copy, then rename upon completion. That way a power outage or
> other mishap won't leave you with scrambled data.

Bob, Yes, that's neat.  I was thinking along those lines slightly
differently.  Running through the file, finding the smallest, writing that to
file B and deleyeing it form file A..
The repeat the search for the smallest etc etc.  Comes to much the same
thing!
Yes, of course make a copy!

Thanks.
G

.