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#!/usr/bin/perl
#
# Perl Weekly Challenge - 071
#
# Task #2: Trim Linked List
#
# https://perlweeklychallenge.org/blog/perl-weekly-challenge-071/
#
package Node;
use Moo;
has v => (is => 'rw');
has p => (is => 'rw');
has s => (is => 'rw');
sub trim {
my ($self, $position) = @_;
die "ERROR: Invalid position [$position].\n"
unless ($position =~ /^\d+$/);
my $tail = $self;
my $count = 1;
my $node;
while ($tail->p) {
if ($position > $count) {
$node = $tail;
}
elsif ($position == $count) {
if (defined $node) {
# Remove current node by making the
# parent of current node as parent
# of previous node
$node->p($tail->p);
}
else {
# If you're taking first from the end
# then return the parent of last node
return $tail->p;
}
}
$tail = $tail->p;
$count++;
}
# Take the first node off if and only if:
# a) you reached the first node or
# b) given position is more than the total nodes
$node->p(undef) if ($count <= $position);
return $self;
}
sub show {
my ($self) = @_;
my $node = $self;
my @v = ();
while ($node->p) {
push @v, $node->v;
$node = $node->p;
}
push @v, $node->v;
$self->s(join ' -> ', reverse @v);
return $self;
}
sub say {
my ($self) = @_;
print $self->s, "\n";
}
package main;
my $L = $ARGV[0] || '1 -> 2 -> 3 -> 4 -> 5';
my $N = $ARGV[1] || 2;
create_linked_list($L)->trim($N)->show->say;
#
#
# METHOD
sub create_linked_list {
my ($list) = @_;
$list =~ s/\s+//g;
die "ERROR: Invalid list [$list].\n"
if ($list !~ /\-\>/);
$list = [ split /\-\>/, $list ];
my $node = Node->new(v => pop @$list);
my $tail = $node;
while (@$list) {
my $node = Node->new(v => pop @$list);
$tail->p($node);
$tail = $node;
}
$node->show->say;
return $node;
}
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