Step by Step solution about How to resolve the algorithm Day of the week step by step in the C++ programming language

This C++ program uses modern C++20 features, including ranges and views, to calculate and print the years from 2008 to 2120 where Christmas (December 25th) falls on a Sunday. Here's a detailed explanation of the code:

1. #include <chrono> and #include <ranges>: These lines include the necessary C++20 standard library headers for working with dates, times, and ranges.

2. std::cout << "Yuletide holidays must be allowed in the following years:\n";: This line prints the introductory message indicating that the program will list the years where Christmas falls on a Sunday.

3. for (int year : std::views::iota(2008, 2121) | std::views::filter([](auto year) { ... })):

   • std::views::iota(2008, 2121) creates a range of integers from 2008 to 2120 (inclusive).
   • std::views::filter applies a filter to the range, keeping only the years that meet a specific condition. The condition is specified within the lambda function.

4. Inside the lambda function:

   • std::chrono::year{year}/std::chrono::December/25 creates a std::chrono::date object representing December 25th of the given year.
   • std::chrono::weekday{} gets the weekday for the specified date.
   • The expression std::chrono::weekday{ ... } == std::chrono::Sunday checks if the weekday is Sunday. If true, it means Christmas falls on Sunday for that year, and the year is kept in the filtered range.

5. std::cout << year << '\n';: For each year that passes the filter, this line prints the year to the console.

The program loops through the years from 2008 to 2120, checking which years have Christmas falling on a Sunday. It then prints the list of years where this condition is met. The output will show the years where Yuletide holidays are allowed, i.e., when Christmas is on a Sunday.

#include <chrono>
#include <ranges>
#include <iostream>

int main() {
    std::cout << "Yuletide holidays must be allowed in the following years:\n";
    for (int year : std::views::iota(2008, 2121)
               | std::views::filter([](auto year) {
                    if (std::chrono::weekday{
                            std::chrono::year{year}/std::chrono::December/25}
                            == std::chrono::Sunday) {
                        return true;
                    }
                    return false;
                })) {
        std::cout << year << '\n';
    }
}