C - 如何仅从周数和年份获取一周内的日期？

Question

我希望函数 return 一个字符串数组，其中每个日期都表示为“13/11”或我可以从中提取日期和月份的任何其他格式。
也许它看起来像这样：

char** get_dates_from_year_and_week(int year, int week) {
    //Magic happens
    return arr
}

get_dates_from_year_and_week(2021, 45);
//Would return ["08/11", "09/11", 10/11", "11/11", "12/11", "13/11", "14/11"];

这怎么可能用c获得？欢迎任何图书馆。

Answer 1

要将 year/week/(day-of-the-week) 转换为 year/month/day，找到一年中第一个星期一的日期作为 ISO 8601 week-of -一年从星期一开始。然后加上 week*7 天。使用 mktime() 确定星期几（自星期日起）并将超出范围的日期纳入其主要范围。

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

typedef struct {
  int year, month, day;
} ymd;

typedef struct {
  int year, week, dow; // ISO week-date: year, week 1-52,53, day-of-the-week 1-7
} ISO_week_date;

int ISO_week_date_to_ymd(ymd *y, const ISO_week_date *x) {
  // Set to noon, Jan 4 of the year.
  // Jan 4 is always in the 1st week of the year
  struct tm tm = {.tm_year = x->year - 1900, .tm_mon = 0, .tm_mday = 4,
      .tm_hour = 12};
  // Use mktime() to find the day-of-the week
  if (mktime(&tm) == -1) {
    return -1;
  }
  // Sunday to Jan 4
  int DaysSinceSunday = tm.tm_wday;
  // Monday to Jan 4
  int DaysSinceMonday = (DaysSinceSunday + (7 - 1)) % 7;
  tm.tm_mday += (x->dow - 1) + (x->week - 1) * 7 - DaysSinceMonday;
  if (mktime(&tm) == -1) {
    return -1;
  }
  y->year = tm.tm_year + 1900;
  y->month = tm.tm_mon + 1;
  y->day = tm.tm_mday;
  return 0;
}

“字符串数组”--> 把那部分留给 OP 去做。

C - 如何仅从周数和年份获取一周内的日期？

C - How to get dates in a week from only weeknumber and year?

c

time