Doomsday rule: Difference between revisions
Add C++
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February 12, 2077 will be on a Friday.
April 2, 2101 will be on a Saturday.</pre>
=={{header|C++}}==
<lang cpp>#include <iostream>
#include <cstdint>
struct Date {
std::uint16_t year;
std::uint8_t month;
std::uint8_t day;
};
constexpr bool leap(int year) {
return year%4==0 && (year%100!=0 || year%400==0);
}
const std::string& weekday(const Date& date) {
static const std::uint8_t leapdoom[] = {4,1,7,2,4,6,4,1,5,3,7,5};
static const std::uint8_t normdoom[] = {3,7,7,4,2,6,4,1,5,3,7,5};
static const std::string days[] = {
"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Saturday"
};
unsigned const c = date.year/100, r = date.year%100;
unsigned const s = r/12, t = r%12;
unsigned const c_anchor = (5 * (c%4) + 2) % 7;
unsigned const doom = (s + t + t/4 + c_anchor) % 7;
unsigned const anchor = (leap(date.year) ? leapdoom : normdoom)[date.month-1];
return days[(doom+date.day-anchor+7)%7];
}
int main(void) {
const std::string months[] = {"",
"January", "February", "March", "April", "May", "June",
"July", "August", "September", "October", "November", "December"
};
const Date dates[] = {
{1800,1,6}, {1875,3,29}, {1915,12,7}, {1970,12,23}, {2043,5,14},
{2077,2,12}, {2101,4,2}
};
for (const Date& d : dates) {
std::cout << months[d.month] << " " << (int)d.day << ", " << d.year;
std::cout << (d.year > 2021 ? " will be " : " was ");
std::cout << "on a " << weekday(d) << std::endl;
}
return 0;
}</lang>
{{out}}
<pre>January 6, 1800 was on a Monday
March 29, 1875 was on a Monday
December 7, 1915 was on a Tuesday
December 23, 1970 was on a Wednesday
May 14, 2043 will be on a Thursday
February 12, 2077 will be on a Friday
April 2, 2101 will be on a Saturday</pre>
=={{header|Cowgol}}==
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