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bacek (8813)

bacek
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Journal of bacek (8813)

Wednesday December 24, 2008
01:11 AM

First post.

[ #38146 ]

Hi.

In response to Pm's "Scripting games in Perl6" I've decided to implement some of them in Perl6.

Let's start with easiest "2008: Beginners Event 1"

Task is to calculate number of different pairs of cards.

    sub fact($n) {
            $n <= 1 ?? 1 !! $n*fact($n-1);
    }

    sub calculate_pairs(@pairs) {
            my %h;
            # Calculate number of distinct cards.
            ++%h{$_} for @pairs;
            # Sum of C^N_2
            [+] map { int(fact($^a) / 2) }, %h.values;
    };

Trivial mathematical solution: number of different pairs for given amount of cards is C^n_2. So, I group cards, calculate number of combinations in different group and sum them.

Little trick: if number of cards in group equals to 1 than int(...) will return 0.

Update: masak++ for pointing to use.perl.org strange reaction on <=

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