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#!/usr/bin/env perl
#
# ch-2.pl - Vowel strings
#
# Ryan Thompson <rjt@cpan.org>
use 5.010;
use warnings;
use strict;
# Follow rules. Basically graph edges.
my %edges = ( a => ['i','e'], e => ['i'], i => ['u','o','e','a'],
o => ['u','a'], u => ['e','o'] );
# Builds vowel strings using BFS with queue
sub vowel_string {
my ($len) = @_;
my @queue = sort keys %edges; # Pre-load queue
my @vstrs;
while (my $str = shift @queue) {
push @vstrs, $str and next if $len <= length $str;
push @queue, $str.$_ for @{$edges{ substr $str, -1 }}
}
@vstrs;
}
# Iterator version
sub vowel_iter {
my ($len) = @_;
my @queue = sort keys %edges;
sub {
while (my $str = shift @queue) {
return $str if $len <= length $str;
push @queue, $str.$_ for @{$edges{ substr $str, -1 }}
}
}
}
say for vowel_string(6);
my $it = vowel_iter(3);
say while $_ = $it->();
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