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C++: Five Weekends

Bjarne-stroustrup
 

The month of October in 2010 has five Fridays, five Saturdays, and five Sundays.

The task

  1. Write a program to show all months that have this same characteristic of five full weekends from the year 1900 through 2100 (Gregorian calendar).
  2. Show the number of months with this property (there should be 201).
  3. Show at least the first and last five dates, in order.

Algorithm suggestions

  • Count the number of Fridays, Saturdays, and Sundays in every month.
  • Find all of the 31-day months that begin on Friday.
#include <vector>
#include <boost/date_time/gregorian/gregorian.hpp>
#include <algorithm>
#include <iostream>
#include <iterator>
using namespace boost::gregorian ;

void print( const date &d ) {
	std::cout << d.year( ) << "-" << d.month( ) << "\n" ;
}

int main( ) {
	greg_month longmonths[ ] = {Jan, Mar , May , Jul ,
		Aug , Oct , Dec } ;
	int monthssize = sizeof ( longmonths ) / sizeof (greg_month ) ;
	typedef std::vector<date> DateVector ;
	DateVector weekendmonster ;
	std::vector<unsigned short> years_without_5we_months ;
	for ( unsigned short i = 1900 ; i < 2101 ; i++ ) {
		bool months_found = false ; //does a given year have 5 weekend months ?
		for ( int j = 0 ; j < monthssize ; j++ ) {
			date d ( i , longmonths[ j ] , 1 ) ;
			if ( d.day_of_week( ) == Friday ) {  //for the month to have 5 weekends
				weekendmonster.push_back( d ) ;
				if ( months_found == false )
				months_found = true ;
			}
		}
		if ( months_found == false ) {
			years_without_5we_months.push_back( i ) ;
		}
	}
	std::cout << "Between 1900 and 2100 , there are " << weekendmonster.size( )
	<< " months with 5 complete weekends!\n" ;
	std::cout << "Months with 5 complete weekends are:\n" ;
	std::for_each( weekendmonster.begin( ) , weekendmonster.end( ) , print ) ;
	std::cout <<  years_without_5we_months.size( ) << " years had no months with 5 complete weekends!\n" ;
	std::cout << "These are:\n" ;
	std::copy( years_without_5we_months.begin( ) , years_without_5we_months.end( ) ,
	std::ostream_iterator<unsigned short>( std::cout , "\n" ) ) ;
	std::cout << std::endl ;
	return 0 ;
}

SOURCE

Content is available under GNU Free Documentation License 1.2.