如何从C++中的周数中找出一周的第一天的日期

Question

Need a C++ function to find out the date of the first day of week from the week number.

Input : year and week number Output : date [It should be 1st day of that week number]

eg :

• inputs :

  • year – 2017 , week number – 8
    Output: 20th Feb 2017

• inputs:

  • year – 2017 , week number – 10
    Output: `6th March 2017

Answer 1

Using Howard Hinnant's free, open-source, header-only date library , it can look like this:

#include "date.h"
#include "iso_week.h"
#include <iostream>

int
main()
{
    using namespace iso_week::literals;
    std::cout << date::year_month_day{2017_y/8_w/mon} << '\n';
    std::cout << date::year_month_day{2017_y/10_w/mon} << '\n';
}

which outputs:

2017-02-20
2017-03-06

There are also getters for year, month and day on the year_month_day types, and plenty of formatting options.