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#! /opt/local/bin/perl
#
# jenga.pl
#
# TASK #2 › Demo Stack
# Submitted by: Mohammad S Anwar
# Write a script to demonstrate Stack operations like below:
#
# push($n) - add $n to the stack
# pop() - remove the top element
# top() - get the top element
# min() - return the minimum element
#
# Example:
#
# my $stack = Stack->new;
# $stack->push(2);
# $stack->push(-1);
# $stack->push(0);
# $stack->pop; # removes 0
# print $stack->top; # prints -1
# $stack->push(0);
# print $stack->min; # prints -1
#
#
# © 2021 colin crain
#
## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
use warnings;
use strict;
use feature ":5.26";
package Node;
use Moo;
has value => ( is => 'rw' );
has down => ( is => 'rw' );
package Stack;
use Moo;
has last => ( is => 'rw' );
sub push {
my ($self, $value) = @_;
my $node = Node->new( value => $value ,
down => $self->last );
$self->last( $node );
};
sub pop {
my $self = shift;
my $node = $self->last;
$self->last( $node->down );
return $node->value;
}
sub top {
my $self = shift;
return $self->last->value;
}
sub min {
my $self = shift;
my $node = $self->last;
my $min = $node->value;
while ( defined $node->down ) {
$min = $node->down->value if $node->down->value < $min;
$node = $node->down;
}
return $min;
}
package main;
my $stack = Stack->new;
$stack->push( 2 );
$stack->push( -1 );
$stack->push( 0 );
$stack->pop; # removes 0
say $stack->top; # prints -1
$stack->push( 0 );
say $stack->min; # prints -1
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