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#https://theweeklychallenge.org/blog/perl-weekly-challenge-237/
use strict; use warnings;
sub the_day {
my($year, $month, $weekday_of_month, $day_of_week) = @_;
my $want_month = $year*100+$month;
my $test_day = ($year-1970)*365+($month-1)*28; #choose a conservative enough start day
while(1) { #Don't Stop 'Til You Get Enough
my @lt = gmtime $test_day++ * 24 * 3600; #get time elems for test_day num, increase test_day
my($se, $mi, $ho, $mday, $m, $y, $dow) = @lt; #y=0 for 1900, m=0 for January
my $test_month = 190001+$y*100+$m; #i.e. 202309 for Sep 2023,
return 0 if $test_month > $want_month; #the wanted month is now passed without a find
return $mday if $test_month == $want_month #same year and month
and $day_of_week%7 == $dow #same weekday, Sun=7=0
and --$weekday_of_month == 0 #the wanted count
}
}
my @tests = (
'{Year => 2024, Month => 4, Weekday_of_month => 3, Day_of_week => 2}' => 16, #The 3rd Tue_of_Apr 2024 is the 16th
'{Year => 2025, Month => 10, Weekday_of_month => 2, Day_of_week => 4}' => 9, #The 2nd Thu_of_Oct 2025 is the 9th
'{Year => 2026, Month => 8, Weekday_of_month => 5, Day_of_week => 3}' => 0, #There isn't a 5th Wed in Aug 2026
'{Year => 1970, Month => 1, Weekday_of_month => 4, Day_of_week => 7}' => 25, #25th was 4th Sun in Jan 1970
'{Year => 1970, Month => 1, Weekday_of_month => 5, Day_of_week => 5}' => 30, #30th was 5th Fri in Jan 1970
);
while(@tests){
my($data, $expected) = splice@tests,0,2;
my $got = the_day( @{eval$data}{qw(Year Month Weekday_of_month Day_of_week)} );
print $got == $expected ? 'ok' : '***NOT OK';
print " data: $data expected: $expected got: $got\n";
}
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