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* [Solution] Project euler challenge 19 with tests * update leap year function * Remove unnecessary, confusingly placed comments --------- Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
49 lines
1.5 KiB
JavaScript
49 lines
1.5 KiB
JavaScript
/**
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* Problem 19 - Counting Sundays
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*
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* @see {@link https://projecteuler.net/problem=19}
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*
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* You are given the following information, but you may prefer to do some research for yourself.
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* 1 Jan 1900 was a Monday.
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* Thirty days has September,
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* April, June and November.
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* All the rest have thirty-one,
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* Saving February alone,
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* Which has twenty-eight, rain or shine.
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* And on leap years, twenty-nine.
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* A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
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* How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?
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*
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* @author ddaniel27
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*/
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import { isLeapYear } from '../Maths/LeapYear'
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function problem19() {
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let sundaysCount = 0 // Count of Sundays
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let dayOfWeek = 2 // 1st Jan 1900 was a Monday, so 1st Jan 1901 was a Tuesday
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for (let year = 1901; year <= 2000; year++) {
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for (let month = 1; month <= 12; month++) {
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if (dayOfWeek === 0) {
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// If it's a Sunday (0 is Sunday, 1 is Monday, ..., 6 is Saturday)
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sundaysCount++
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}
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let daysInMonth = 31
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if (month === 4 || month === 6 || month === 9 || month === 11) {
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// April, June, September, November
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daysInMonth = 30
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} else if (month === 2) {
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// February
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daysInMonth = isLeapYear(year) ? 29 : 28
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}
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dayOfWeek = (dayOfWeek + daysInMonth) % 7 // Calculate the day of the week
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}
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}
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return sundaysCount
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}
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export { problem19 }
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