Subj : Re: Sorting
To   : borland.public.cpp.borlandcpp
From : Bob Gonder <notbg@notmindspring.invalid>
Date : Tue Dec 09 2003 09:41 am

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.

.