#!/usr/bin/perl
use strict;
use warnings;
use Storable;

my ($src, $tgt) = @ARGV;
die "Usage: $0 <src> <tgt>" if ! defined $src || ! defined $tgt;
die "The <src> and <tgt> must be same length" if length($src) != lengt
+h($tgt);

my $db = retrieve('dictionary.db');
my $path = find_path($src, $tgt, $db->{length($tgt)});
print "$path\n";

sub find_path {
    my ($src, $tgt, $list, $seen, $work) = @_;
    @$work = map {key => $_ => path => "$src->$_"}, @{$list->{$src}} i
+f ! defined $work;
    my $next = [];    
    for (@$work) {
        my ($word, $path) = @{$_}{qw/key path/};
        next if $seen->{$word}++;
        return $path if $word eq $tgt;
        push @$next, map {key => $_, path => "$path->$_"}, @{$list->{$
+word}};
    }
    return find_path($src, $tgt, $list, $seen, $next) if @$next;
    return 'path not found';
}
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#!/usr/bin/perl
use strict;
use warnings;
use Storable;
use Text::LevenshteinXS 'distance';

my ($src, $tgt) = @ARGV;
die "Usage: $0 <src> <tgt>" if ! defined $src || ! defined $tgt;
die "The <src> and <tgt> must be same length" if length($src) != lengt
+h($tgt);

my $db = -e 'dictionary.db' ? retrieve('dictionary.db') : build_db();
my $list = check_db($src, $tgt, $db);
die $list if ! ref $list;

my $path = find_path($src, $tgt, $list);
print "$path\n";

sub find_path {
    my ($src, $tgt, $list, $seen, $work) = @_;
    @$work = map {key => $_ => path => "$src->$_"}, @{$list->{$src}} i
+f ! defined $work;
    my $next = [];
    for (@$work) {
        my ($word, $path) = @{$_}{qw/key path/};
        next if $seen->{$word}++;
        return $path if $word eq $tgt;
        push @$next, map {key => $_, path => "$path->$_"}, @{$list->{$
+word}};
    }
    return find_path($src, $tgt, $list, $seen, $next) if @$next;
    return 'path not found';
}

sub check_db {
    my ($src, $tgt, $db) = @_;
    my $len = length($tgt);
    return "Unable to work with $tgt" if ! exists $db->{$len};
    for my $word ($src, $tgt) {
        if (! exists $db->{$len}{$word}) {
            for (grep distance($_, $word) == 1, keys %{$db->{$len}}) {
                push @{$db->{$len}{$word}}, $_;
                push @{$db->{$len}{$_}}, $word;
            }
            return "Unable to work with $word" if ! @{$db->{$len}{$wor
+d}};
        }
    }
    return $db->{$len};
}

# Runs once and can be removed after DB is built
sub build_db {
    open (my $dict, '<', '2of12.txt') or die "Unable to open '2of12.tx
+t' for reading: $!";
    my ($db, %data);

    while (<$dict>) {
        chomp;
        push @{$data{length()}}, $_;
    }
    for my $len (keys %data) {
        my $end = $#{$data{$len}};
        for my $i (0 .. $end - 1) {
            my $word = $data{$len}[$i];
            for my $j ($i + 1 .. $end) {
                my $test = $data{$len}[$j];
                ! exists $db->{$len}{$_} and $db->{$len}{$_} = [] for 
+$word, $test;
                if (distance($word, $test) == 1) {
                    push @{$db->{$len}{$word}}, $test;
                    push @{$db->{$len}{$test}}, $word;
                }
            }
        }
    }
    store $db, 'dictionary.db';
    return retrieve('dictionary.db');
}
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