perl/p5.pl


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#!/usr/bin/env perl

use strict;
use warnings;

use List::Util qw(reduce max all);

# Functional

# Imperative
my @primes = (2);
sub factorize {
	my $n = shift;
	for my $i ($primes[-1] .. $n) {
		push @primes, $i if all { $i % $_ != 0 } @primes;
	}
	my $factors;
	for my $prime (@primes) {
		if ($n % $prime == 0) {
			$factors->{$prime}++;
			$n /= $prime;
			redo;
		}
	}
	return $factors;
}

sub merge_factors {
	my $fst = shift;
	my $snd = shift;
	my $res;
	foreach my $k (keys %$fst) {
		$res->{$k} = max($res->{$k} || 0, $fst->{$k});
	}
	foreach my $k (keys %$snd) {
		$res->{$k} = max($res->{$k} || 0, $snd->{$k});
	}
	return $res;
}

my @factors = map { factorize $_ } (2..20);
my $mcm = reduce { merge_factors($a, $b) } @factors;

my $res = 1;
foreach my $k (keys %$mcm) {
	$res *= $k ** $mcm->{$k};
}
print $res, "\n";