/* Count the Weekend Days Given a date, either past or future, provided by the user, output the weekend days that could be enjoyed. The only library code allowed is to retrive the current date and day of the week. Your code must perform all calculations. If today is a weekend day, it does not count. If the day given by the user is a weekend day, it does count. The date input format is up to you, but must be documented by comments. You must support all dates between 2010 and 2030. You must document any limits on dates in comments. Given today is the 21st of July 2020 and the user entered the 10th of June 2020, the answer is 12. If they gave 10th of August 2020, the answer is 6. This site does many calculation you can use to verify your code. https://www.timeanddate.com/date/workdays.html https://code.sololearn.com/cZ8CbO6mbXik */ #include #include #include #include #include using namespace std; // maximum number of years. Just any arbitary // value constexpr int MYEAR = 5000; // Date format is mm/dd/yyyy struct Date { int month{0}; // range 1-12 int day{0}; // day of month int year{0}; int dow{-1}; // day of week (0-6) with 0 // being sunday and 6 being // saturday. // flag to check if the weekend is to be // ignored or not. A weekend is ignored // when the user does not provide one of // dates. In such case we set one of the // date as today's date and check if it is // a weekend or not. If weekend, ignore it. bool to_ignore{false}; // string representation string to_string() const { stringstream ss; ss << month << '/' << day << '/' << year; return ss.str(); } }; struct Calendar { static int mdays[]; // leap year check static bool is_leap(int year) { return !(year % 400) || (year % 100 && !(year % 4)); } // Extract and return new Date object // from string provided. If date string is // empty, we fetch todays date. static Date parse_date(string date_str) { Date date; if (date_str.empty()) { // get today's' date using built // in functions time_t t{time((0))}; struct tm *now{localtime(&t)}; date.year = now->tm_year + 1900; date.month = now->tm_mon + 1; date.day = now->tm_mday; date.dow = get_dow(date); // if today's day is weekend, // then do not // count in calculations; // 5 is saturday and 0 is sunday if (date.dow == 5 || date.dow == 0) date.to_ignore = true; return date; } char _; // dummy char for consuming '/' stringstream ss{date_str}; ss >> date.month >> _ >> date.day >> _ >> date.year; // validate the specified date, throw // exception if values out of range if (!is_valid_date(date)) throw out_of_range("Date value" " supplied are out of valid" " range."); // get day of the week date.dow = get_dow(date); return date; } // check the validity of date object // year range 1 to 5000 (inclusive) // month range 1 to 12 (inclusive) // day range, as mentioned in lookup table static bool is_valid_date(Date const & date) { return ( date.year >= 1 && date.year <= MYEAR) && (date.month >= 1 && date.month <= 12) && (date.day >= 1 && date.day <= get_month_days(date)); } // Calculate the number of days in a // month, while taking care of leap year static int get_month_days(Date const &date) { return date.month == 2 ? mdays[date.month] + is_leap(date.year) : mdays[date.month]; } // Find the day of the week // https://en.m.wikipedia.org/wiki/Determination_of_the_day_of_the_week static int get_dow(Date const &date) { // offsets of starting day of the month static int off[] = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4}; int yr{date.year}; yr -= (date.month < 3); return (yr + yr / 4 - yr / 100 + yr / 400 + off[date.month - 1] + date.day) % 7; } // get the date in terms of total days // multiply the year by 365 and add the // current month day offset. Then add // all months days before current month static int get_date_in_days(Date const & d) { // running sum of days after each month // 1 based index for easy calculations static int days_sum[] {0, 31, 59, 90, 120, 151,181, 212, 243, 273, 304, 334}; int total_days = 365 * d.year + d.day; auto count_lp_years = [=]( auto const &date) { int yr{date.year}; // check if current year needs to be // considered if (date.month < 3) yr--; // leap year is divisible by 4 // and 400 but not by 100 return yr / 4 - yr / 100 + yr / 400; }; return total_days + days_sum[d.month-1] + count_lp_years(d); } // returns the difference between two // dates in terms of days static int get_diff_bw_two_dates( Date const& sdate, Date const& edate) { // +1 for including the last date return get_date_in_days(edate) - get_date_in_days(sdate) + 1; } // Calculate Weekends static int get_weekends_bw_dates(Date const& sdate, Date const& edate) { int diff_days = get_diff_bw_two_dates(sdate, edate); // full weeks int tweeke = 2 * (diff_days / 7); // get the remaing days if any. // Then loop till that many days // and starting from start date's // dow, update remaining dow table. // Then add count of sunday and // saturday to tweeke count. Sunday // is at off[0] and saturday at // off[6] int rem_days = diff_days % 7; int off[7]{}; for(int i=0; i < rem_days; ++i) off[(sdate.dow+i)%7]++; tweeke += off[0] + off[6]; // subtract if the dates are to // be ignored return tweeke - sdate.to_ignore - edate.to_ignore; } }; // out of class static data initialization // representing number of days in a normal year. int Calendar :: mdays[]{ 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; // overloading '>' operator to find earlier date bool operator > (Date const& sdate, Date const& edate) { return Calendar::get_date_in_days(sdate) > Calendar::get_date_in_days(edate) ? true : false; } // Helper function // sdate is user provided start date // edate is user provided end date // The function will swap start and end dates if // required so as to ensure start date is always // earlier date void calculate_weekends(string const& sdatestr, string const& edatestr) { Date sdate = Calendar::parse_date(sdatestr); Date edate = Calendar::parse_date(edatestr); // ensure sdate is an earlier date if(sdate > edate ) swap(sdate, edate); cout << "Total number of weekends" << " between start date " << sdate.to_string() << " and end date (inclusive) " << edate.to_string() << " are : " << Calendar :: get_weekends_bw_dates(sdate, edate); } int main() { string start_date, end_date; // empty values allowed in that case today's // date will be used cin >> start_date >> end_date; try { calculate_weekends(start_date, end_date); } catch (out_of_range const &e) { cout << e.what() << "\n\n" << "Using defaults\n"; string start_date{"6/10/2020"}; string end_date{"7/26/2020"}; calculate_weekends(start_date, end_date); } }

[Challenge] Weekends_Between_Two_Dates.cpp