Re: One for the weekend: challenge

[Anonymous Monk]

This took about two hours to write, through three iterations to get reasonable performance (under one second on a Sempron 3000). I'm sure I'll have issues with the "maintainability" score :)

#!perl
use strict;
my %dict;
@ARGV = qw( d.dict d.input );

while(<>) # read in both files, load dict on first, match on second
  {
  chomp;
  (my $d = lc) =~ tr|a-z"/-|57630499617851881234762239|d;
  $ARGV eq 'd.dict' ?  push @{$dict{$d}}, $_ : match($d, 0, "$_:");
  }

sub match # (to match, last was digit, matches)
  {
  my ($in, $digit, @have, $cnt) = @_;
  $in eq '' and return print "@have\n"; # have full match
  for my $k (map { substr $in, 0, $_ } 2..length $in)
    {
    match(substr($in, length $k), !++$cnt, @have, $_) for @{$dict{$k}}
+;
    }
  $cnt or $digit or match(substr($in, 1), 1, @have, substr $in, 0, 1);
  }

[karavelov]

Amazing! It runs very fast! Here it runs for 0,6 seconds on the standard set of 1000 numbers (compared to 2.2 sec my code). With growing the set of numbers they are comparable in speed - for 50000 numbers they are equal 13.7 seconds. It seems that I am hurt by the regex compile time.

I think your code is better than mine because :
1. you do not relay on some experimental features and recent optimizations;
2. The difference is in how we get the possible correct continuations of the number. My code generates them with the hairy regular expression. Your code generates all possible continuations and filter only the correct ones trough hash lookup.
3. less is more

Best regards

[BrowserUk]

Utterly, utterly amazing.

As presented, I think you would have to acquire a few maintainability demerits, but I don't think that it would be that hard to clean it up, and I don't think the result would hurt your timing or LOC unduly.

[Anonymous Monk]

Remember when considering "maintainability" that the shorter the program, the easier it is to understand :)

/me ducks

[Anonymous Monk]

Slightly faster :)

#!perl
use strict;
my %dict;
@ARGV = qw( d.dict d.input );

while(<>) # read in both files, load dict on first, match on second
  {
  chomp;
  (my $d = lc) =~ tr|a-z"/-|57630499617851881234762239|d;
  @ARGV ? push @{$dict{$d}}, $_ : match($d, 0, "$_:");
  }

sub match # (to match, last was digit, matches)
  {
  my ($in, $digit, @have, $k) = @_;
  map match(substr($in, $k), !++$digit, @have, $_),
    @{$dict{substr $in, 0, $k = $_}} for 2..length $in;
  $in =~ s/(.)// ? $digit || match($in, 1, @have, $1) : print "@have\n
+";
  }