|
| 1 | +/** |
| 2 | + * Problem 19 - Counting Sundays |
| 3 | + * |
| 4 | + *@see {@link https://projecteuler.net/problem=19} |
| 5 | + * |
| 6 | + * You are given the following information, but you may prefer to do some research for yourself. |
| 7 | + * 1 Jan 1900 was a Monday. |
| 8 | + * Thirty days has September, |
| 9 | + * April, June and November. |
| 10 | + * All the rest have thirty-one, |
| 11 | + * Saving February alone, |
| 12 | + * Which has twenty-eight, rain or shine. |
| 13 | + * And on leap years, twenty-nine. |
| 14 | + * A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400. |
| 15 | + * How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)? |
| 16 | + * |
| 17 | + *@author ddaniel27 |
| 18 | + */ |
| 19 | +import{isLeapYear}from'../Maths/LeapYear' |
| 20 | + |
| 21 | +functionproblem19(){ |
| 22 | +letsundaysCount=0// Count of Sundays |
| 23 | +letdayOfWeek=2// 1st Jan 1900 was a Monday, so 1st Jan 1901 was a Tuesday |
| 24 | + |
| 25 | +for(letyear=1901;year<=2000;year++){ |
| 26 | +for(letmonth=1;month<=12;month++){ |
| 27 | +if(dayOfWeek===0){ |
| 28 | +// If it's a Sunday (0 is Sunday, 1 is Monday, ..., 6 is Saturday) |
| 29 | +sundaysCount++ |
| 30 | +} |
| 31 | + |
| 32 | +letdaysInMonth=31 |
| 33 | +if(month===4||month===6||month===9||month===11){ |
| 34 | +// April, June, September, November |
| 35 | +daysInMonth=30 |
| 36 | +}elseif(month===2){ |
| 37 | +// February |
| 38 | +daysInMonth=isLeapYear(year) ?29 :28 |
| 39 | +} |
| 40 | + |
| 41 | +dayOfWeek=(dayOfWeek+daysInMonth)%7// Calculate the day of the week |
| 42 | +} |
| 43 | +} |
| 44 | + |
| 45 | +returnsundaysCount |
| 46 | +} |
| 47 | + |
| 48 | +export{problem19} |