RabbitFarm

The examples used here are from The Weekly Challenge problem statement and demonstrate the working solution.

Part 1

You are given a list of numbers. Write a script to implement JortSort. It should return true/false depending if the given list of numbers are already sorted.

Solution

use strict;
use warnings;
use boolean;

sub jort_sort{
    for(my $i=0; $i < @_ - 1; $i++){
        return false if $_[$i + 1] < $_[$i];  
    }  
    return true;
}

MAIN:{
    print jort_sort(1, 2, 3, 4, 5) . "\n";
    print jort_sort(1, 3, 2, 4, 5) . "\n";
}

Sample Run

$ perl perl/ch-1.pl
1
0

Notes

Apparently Jort Sort is a joke sort started by somebody in the JavaScript community. I didn't find it all that funny, but the code to implement it only took a quick minute.

Part 2

Write a script to generate the first 5 Long Primes.

Solution

use strict;
use warnings;
use boolean;
use LWP::UserAgent;
use constant PRIME_URL => "http://primes.utm.edu/lists/small/100000.txt";

sub get_primes{
    my @primes;  
    my $ua = new LWP::UserAgent(
        ssl_opts => {verify_hostname => 0}
    );
    my $response = $ua->get(PRIME_URL);
    my @lines = split(/\n/,$response->decoded_content);
    foreach my $line (@lines){
        my @p = split(/\s+/, $line);
        unless(@p < 10){
            push @primes, @p[1..(@p - 1)]; 
        }  
    }
    return @primes; 
}

sub divide{
    my($n, $d) = @_; 
    my @remainders;
    my $q = (int($n / $d)) . ".";
    my $r = $n % $d; 
    push @remainders, $r; 
    my @a;
    for (0 .. $d){
        $q .= int($r*10 / $d);  
        $r = $r*10 % $d;
        @a = grep { $remainders[$_] == $r } (0 .. @remainders - 1);
        last if(@a); 
        push @remainders, $r; 
    }
    my $r_i = $a[0];
    my $i = index($q, ".");
    my $decimal_part = substr($q, $i+1); 
    return substr($q, 0, $i + 1) . substr($decimal_part, 0, $r_i) . "(" . substr($q, $i + $r_i + 1) . ")";  
}   

sub long_primes_five{
    my @long_primes;
    my @primes = get_primes();
    do{
        my $prime = shift @primes;    
        my $max_repetend = $prime - 1; 
        my $repeats = true if($prime != 2 && $prime != 5); 
        if($repeats){
            my $x = divide(1, $prime, [], []); 
            $x =~ m/\((\d+)\)/;
            my $repetend = $1;
            push @long_primes, [$prime, $x] if length($repetend) == $prime - 1;   
        }
    }while(@long_primes < 5);
    return @long_primes;
}

MAIN:{
    for my $p (long_primes_five()){
        print $p->[0] . "\t" . $p->[1] . "\n";
    }
}

Sample Run

$ perl perl/ch-2.pl 
7       0.(142857)
17      0.(0588235294117647)
19      0.(052631578947368421)
23      0.(0434782608695652173913)
29      0.(0344827586206896551724137931)

Notes

This second part of the challenge was much more fun! Maybe my favorite part was that it largely re-used code from challenge 106 and also Challenge 015. Here we grab a list of pre-computed primes and then check each one for the desired property. After we find five, as required, we're done.

References

Jort Sort

Long Prime

Challenge 139