[Solution] Project euler challenge 19 with tests by ddaniel27 · Pull Request #1659 · TheAlgorithms/JavaScript

@@ -0,0 +1,48 @@ /** * Problem 19 - Counting Sundays * * @see {@link https://projecteuler.net/problem=19} * * You are given the following information, but you may prefer to do some research for yourself. * 1 Jan 1900 was a Monday. * Thirty days has September, * April, June and November. * All the rest have thirty-one, * Saving February alone, * Which has twenty-eight, rain or shine. * And on leap years, twenty-nine. * A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400. * How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)? * * @author ddaniel27 */ import { isLeapYear } from '../Maths/LeapYear'
function problem19() { let sundaysCount = 0 // Count of Sundays let dayOfWeek = 2 // 1st Jan 1900 was a Monday, so 1st Jan 1901 was a Tuesday
for (let year = 1901; year <= 2000; year++) { for (let month = 1; month <= 12; month++) { if (dayOfWeek === 0) { // If it's a Sunday (0 is Sunday, 1 is Monday, ..., 6 is Saturday) sundaysCount++ }
let daysInMonth = 31 if (month === 4 || month === 6 || month === 9 || month === 11) { // April, June, September, November daysInMonth = 30 } else if (month === 2) { // February daysInMonth = isLeapYear(year) ? 29 : 28 }
dayOfWeek = (dayOfWeek + daysInMonth) % 7 // Calculate the day of the week } }
return sundaysCount }
export { problem19 }