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#include <stdio.h>
#define NDEBUG
#include <assert.h>
static char daytab[2][13] = {
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
/* day_of_year: set day of year from month & day */
int day_of_year(int year, int month, int day)
{
assert(month >= 1);
assert(month <= 12);
int i, leap;
leap = (year%4 == 0 && year%100 != 0) || year%400 == 0;
assert(day >= 1);
assert(day <= *(*(daytab+leap) + month));
for (i = 1; i < month; i++)
day += *(*(daytab+leap) + i);
return day;
}
/* month_day: set month, day from day of year */
void month_day(int year, int yearday, int *pmonth, int *pday)
{
int i, leap;
leap = (year%4 == 0 && year%100 != 0) || year%400 == 0;
assert(yearday >= 1);
assert(yearday <= (leap ? 366 : 365));
for (i = 1; yearday > *(*(daytab+leap)+i); i++)
yearday -= *(*(daytab+leap)+i);
*pmonth = i;
*pday = yearday;
}
int main(void) {
// Add error checking eh
int doy, dom, month;
doy = day_of_year(2022, 2, 8);
month_day(2022, doy, &month, &dom);
printf("2022-02-08 doy=%d month=%d dom=%d\n", doy, month, dom);
doy = day_of_year(2022, 0, 8);
doy = day_of_year(2022, 13, 8);
doy = day_of_year(2022, 12, 0);
doy = day_of_year(2022, 12, 32);
doy = day_of_year(2022, 2, 29);
doy = day_of_year(2024, 2, 29); // This one is ok
}
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