project-euler/Sidef/019 Counting Sundays.sf

#!/usr/bin/ruby

# Author: Daniel "Trizen" Șuteu
# License: GPLv3
# Website: https://github.com/trizen

# How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

# https://projecteuler.net/problem=19

# Runtime: 0.446s

require('DateTime')

func first_sundays(year) {
    var count = 0
    for i in (1..12) {

        var date = %O<DateTime>.new(
            year  => year,
            month => i,
            day   => 1,
        )

        ++count if (date.dow == 7)
    }
    return count
}

var total = 0
for year in (1901 .. 2000) {
    total += first_sundays(year)
}
say total