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|
#!/usr/bin/perl
use warnings;
use strict;
use feature qw( say );
use Math::Combinatorics;
# Write a program to solve Knapsack Problem.
# Solution: Create a self packing Knapsack object that fills itself with the best combination of boxes.
# This code solves for both cases of box availability: use each box once or reuse box types up to count and weight limits.
my $capacity = shift;
my $box_reuse = shift;
do {
print <<EOU;
Usage:
$0 capacity reuse-box
$0 15 1
$0 15 0
EOU
exit;
} unless $capacity;
my $BOX = { # Global data structure
R => { weight => 1, amount => 1 },
B => { weight => 1, amount => 2 },
G => { weight => 2, amount => 2 },
Y => { weight =>12, amount => 4 },
P => { weight => 4, amount =>10 },
};
my @box = (sort keys %$BOX);
say "Problem:";
say "Box\tWeight\tAmount";
foreach my $box (@box) {
say "$box\t$BOX->{$box}{weight}\t$BOX->{$box}{amount}";
}
# Create new Knapsack, pack it and say best fit for all $c combinations: 2, 3, 4 and 5 boxes
my $knapsack;
my $c;
my $out = $box_reuse ? "box types" : "boxes limit";
say "\nSolution: (2 $out)";
$knapsack = Knapsack->new($capacity,2,$box_reuse);
$c = Math::Combinatorics->new(count => 2, data => [@box]);
while (my @combo = $c->next_combination) {
$knapsack->pack(@combo);
}
$knapsack->box_list();
say "\nSolution: (3 $out)";
$knapsack = Knapsack->new($capacity,3,$box_reuse);
$c = Math::Combinatorics->new(count => 3, data => [@box]);
while (my @combo = $c->next_combination) {
$knapsack->pack(@combo);
}
$knapsack->box_list();
say "\nSolution: (4 $out)";
$knapsack = Knapsack->new($capacity,4,$box_reuse);
$c = Math::Combinatorics->new(count => 4, data => [@box]);
while (my @combo = $c->next_combination) {
$knapsack->pack(@combo);
}
$knapsack->box_list();
say "\nSolution: (5 $out)";
$knapsack = Knapsack->new($capacity,5,$box_reuse);
$knapsack->pack(@box);
$knapsack->box_list();
exit;
package Knapsack;
sub new {
my $class = shift;
my $self = {
capacity => shift,
box_max => shift,
box_reuse => shift,
box_list => '', # current state of the object
weight => 0,
amount => 0,
best_list => '', # best state reached
best_weight => 0,
best_amount => 0,
};
bless $self, $class;
return $self;
}
sub pack {
my ($self,@box) = @_;
if ($self->{box_reuse}) {
$self->pack_reuse(@box);
}
else {
$self->pack_solo(@box);
}
}
sub pack_reuse {
my ($self,@box) = @_;
foreach my $box (@box) {
if ($self->box_will_fit($box)) {
$self->box_add($box);
$self->pack_reuse(@box);
$self->box_sub($box);
}
}
}
sub pack_solo {
my ($self,@box) = @_;
foreach my $box (@box) {
next if ($self->{box_list} =~ m/$box/); # can not use same box twice
if ($self->{box_max} > length($self->{box_list})) { # can not exceed number of boxes allowed
if ($self->box_will_fit($box)) {
$self->box_add($box);
$self->pack_solo(@box);
$self->box_sub($box);
}
}
}
}
sub box_add {
my ($self,$box) = @_;
$self->{weight} += $BOX->{$box}{weight};
$self->{amount} += $BOX->{$box}{amount};
$self->{box_list} .= $box;
if ($self->{amount} > $self->{best_amount} ) {
$self->{best_amount} = $self->{amount};
$self->{best_weight} = $self->{weight};
$self->{best_list} = $self->{box_list};
}
}
sub box_sub {
my ($self,$box) = @_;
$self->{weight} -= $BOX->{$box}{weight};
$self->{amount} -= $BOX->{$box}{amount};
chop $self->{box_list};
}
sub box_list {
my $self = shift;
say "Box list: $self->{best_list}";
say "Total weight: $self->{best_weight}";
say "Total amount: $self->{best_amount}";
}
sub box_will_fit {
my ($self,$box) = @_;
return ($self->{capacity} >= $self->{weight} + $BOX->{$box}{weight});
}
1;
__END__
./ch-2.pl
Usage:
./ch-2.pl capacity reuse-box
./ch-2.pl 15 1
./ch-2.pl 15 0
./ch-2.pl 15 1
Problem:
Box Weight Amount
B 1 2
G 2 2
P 4 10
R 1 1
Y 12 4
Solution: (2 box types)
Box list: BBBPPP
Total weight: 15
Total amount: 36
Solution: (3 box types)
Box list: BBBPPP
Total weight: 15
Total amount: 36
Solution: (4 box types)
Box list: PPPBBB
Total weight: 15
Total amount: 36
Solution: (5 box types)
Box list: BBBPPP
Total weight: 15
Total amount: 36
./ch-2.pl 15 0
Problem:
Box Weight Amount
B 1 2
G 2 2
P 4 10
R 1 1
Y 12 4
Solution: (2 boxes limit)
Box list: BP
Total weight: 5
Total amount: 12
Solution: (3 boxes limit)
Box list: BGP
Total weight: 7
Total amount: 14
Solution: (4 boxes limit)
Box list: GRPB
Total weight: 8
Total amount: 15
Solution: (5 boxes limit)
Box list: BGPR
Total weight: 8
Total amount: 15
|
