Hey guys. I decided to do another project euler problem, and got this problem:
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)?After I come up with an algorithm, I normally check it against other one's on the web. Mine oddly seems faster and simpler than all the one's I've seen (never happend befor). I just want to make sure it makes sence, and I'm not missing something. Here is the algorithm:
year = 1901
day = 1 //tuesday
sum = 0
while year is less than 2001
day += 31
sum += day/7 //add the number of sundays in this january to sum
day %= 7 //this is the day that this january end on
if year is divisable by 4 and year is not divisible by 100 //leap year
day += 335
else if year is divisable by 4 and divisable by 100 //leap year
day += 335
else //not leap year
day += 334
day %= 7 //day now equals the first day fo january
year++Is there something I'm missing?
The other algorithms I've seen seem to use the fact that there are 1200 months in a century and requre a counter for day, week, month, year and sum.
Thanks.
