CODEWITHSUNDEEP
perlunique
Steve
Steve

Reputation: 54592

print out unique lines in Perl

I've been challenged with a mathematics problem. Given ten numbers (in this case, numbers from 1 to 10), how many unique combinations of six numbers are there? The short answer is 210. However, I would like to know what these combinations are.

I have put the following code together. The first while loop works fine to create a lot of sorted combinations, however, I haven't been able to print out only the unique line combinations. How can I print out these unique lines?

my %hash;
my @sorted_numbers;

# make all permutations with numbers from 1 to 10
my $permutor = List::Permutor->new (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
while ( my @permutation = $permutor->next() ) {
        my $string = "@permutation";
        my ($N1, $N2, $N3, $N4, $N5, $N6, $N7, $N8, $N9, $N10) = split (/ /, $string);

        # chose only the first six numbers and sort them in ascending order
        my @numbers = ($N1, $N2, $N3, $N4, $N5, $N6);
        @sorted_numbers = sort {$a <=> $b} @numbers;
}

# print out the unique number combinations from the temp file
my @unique_combinations = uniq @sorted_numbers;
foreach ( @unique_combinations ) {
    print $_, "\n";
}

Upvotes: 2

Views: 870

Answers (2)

ErikR
ErikR

Reputation: 52057

(this smells a lot like a homework problem, so I'm only going to give you a hint)

On each iteration you need to store @sorted_numbers some place, e.g.:

while (my @permutation = $permutor->next) {
    ...
    @sorted_numbers = sort { $a <= > $b } @numbers;
    push(@combinations, ...);
}

my @unique_combinations = uniq @combinations;
foreach (@unique_combinations) {  ... }

So you have to figure out what to push onto the list @combinations so that the call to uniq will do what you want.

Some other pointers:

(1,2,3,4,5,6,7,8,9,10) may be written (1..10)

You can compute @numbers directly from @permutation with an array slice:

my @numbers = @permutation[0..5];

Upvotes: 3

FMc
FMc

Reputation: 42421

There are probably other CPAN modules for this, but here's one way:

use Math::Combinatorics qw(combine);
my @comb = combine(6, 1..10);

Upvotes: 4

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