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#!/usr/bin/perl
use strict;
use warnings;
use v5.10;
# And you can change these constants to get the solution for day other than Christmas, or for other day of week
my $currentDayOfWeek = 3;
my $currentYear = 2019;
my $REQUESTED_DAY_OF_WEEK = 0;
my $DAYS_IN_WEEK = 7;
my $DAYS_IN_YEAR = 365;
sub getNextWeekDay {
my ($prevDay, $isLeap) = @_;
my $days = 365 + $isLeap;
return ($prevDay + $days) % $DAYS_IN_WEEK;
}
# And you can change the definition of the leap year, for example, to include centuries in them
sub isLeapYear {
my ($year) = @_;
return $year % 4 > 0
? 0
: $year % 100 > 0
? 1
: $year % 400 == 0;
}
while ($currentYear < 2100) {
my $isLeap = isLeapYear(++$currentYear);
$currentDayOfWeek = getNextWeekDay($currentDayOfWeek, $isLeap);
if ($currentDayOfWeek == $REQUESTED_DAY_OF_WEEK) {
say $currentYear;
}
}
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