On topic: The Wednesday Challenge

Yitzchak Scott-Thoennes sthoenna at efn.org
Wed Aug 15 22:47:23 BST 2007

On Wed, August 15, 2007 7:01 am, Andy Armstrong wrote:
> Given a 64 Mbyte file containing random binary data write a perl
> program such that
> $ perl myprog.pl < 64m.bin > 64m.sorted.bin
> outputs a file 64m.sorted.bin with all the bytes sorted in ascending
> order. Marks will be given for speed, brevity and parsimonious use of
> memory.

Everyone so far has failed on that last point.  My solution (written before
reading the responses):

#!/usr/bin/perl -w
use strict;

$/ = \1024;
my %byte;
map ++$byte{$_}, unpack "(Z)*", $_ while <>;
for my $ch (sort keys %byte) {
   print($ch x ($byte{$ch} % 1024));
   print($ch x 1024) for 1 .. $byte{$ch} / 1024;

(Previous version had unpack "C", @byte instead of %byte, and the ugly
next that cost someone else a point.  Though maybe the sort costs a point

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