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Make an if statement execute an equation and use answer

sethfrias (20)
Hello,

I've been beating my head against a wall running into different error/not having wanted/correct results. This program is supposed to return what day an entered date is attached to.

First problem, if dayOfWeek is >7, I want it to divide the dayOfWeek by 4 and then use the remainder as the number to display what day of the week it is.

Second question, on lines 34-35, I am getting the error uninitialized local variable 'century' and 'yearValue' used. Which is weird to me. If I remove the declarations before I call the functions on lines 33-35 then initialized them just above like I did before, it will compile, but this doesn't seem the correct way to solve it.

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//Using zeller's algorithm
//F=K+((13*M+1)/5)+D+(D/4)+(C/4)-2*C --- Formula
//(F=Day of week), (K=Day of month), (D=Last two digits of year), 
//(C=first two digits of year(century)

#include <iomanip>
#include <iostream>
#include <string>
#include <cmath>
//using namespace std;

bool isLeapYear(int);
int getCenturyValue(int);
int getYearValue(int);
void getInput(int&, int&, int&);
void returnWeekDay(int, std::string, int);

int main() {

	int year = 0;
	int month = 0;
	int day = 0;
	/*int month = int();
	int day = int();*/
	int dayOfWeek = int();
	//int century = int();
	//int yearValue = int();
	std::string weekDay;
	int dayOfWeekRem = int();

	getInput(year, month, day);

	bool leapYear = isLeapYear(year);
	int century = getCenturyValue(century);
	int yearValue = getYearValue(yearValue);

	dayOfWeek = day + ((13 * (month + 1)) / 5) + (yearValue) 
		+ (yearValue / 4) + (century / 4) - (2 * century);

	returnWeekDay(dayOfWeek, weekDay, dayOfWeekRem);

	system("pause");
}

void getInput(int &year, int &month, int &day) {

	std::cout << "Enter a year: ";
	std::cin >> year;
	std::cout << "Enter a month (1-12): \n";
	std::cout << "Jan. = 1\n";
	std::cout << "Feb. = 4\n";
	std::cout << "Mar. = 3\n";
	std::cout << "Apr. = 6\n";
	std::cout << "May. = 1\n";
	std::cout << "Jun. = 4\n";
	std::cout << "Jul. = 6\n";
	std::cout << "Aug. = 2\n";
	std::cout << "Sep. = 5\n";
	std::cout << "Oct. = 0\n";
	std::cout << "Nov. = 3\n";
	std::cout << "Dec. = 5\n";
	std::cin >> month;
	std::cout << "Enter a day (1-31): ";
	std::cin >> day;

}

bool isLeapYear(int year) {

	if (year % 4 == 0) {
		if (year % 100 == 0) {
			if (year % 400 == 0) {
				std::cout << "This year is a leap year.\n";
				return true;
			}
			else {
				std::cout << "This year is not a leap year.\n";
				return false;
			}
		}
		else {
			std::cout << "This year is not a leap year.\n";
			return true;
		}
	}
	/*else {
		std::cout << "This year is not a leap year.\n";
		return false;
	}*/

	return false;

}

int getCenturyValue(int year) {

	return year / 100;

}

int getYearValue(int year) {

	return year % 100;

}

void returnWeekDay(int dayOfWeek, std::string weekDay, int dayOfWeekRem) {

	/*std::string weekDay;
	int dayOfWeek = int();*/

	if (dayOfWeek == 0) {
		std::cout << "This is a Sunday.";
	}
	if (dayOfWeek == 1) {
		std::cout << "This is a Monday.";
	}
	if (dayOfWeek == 2) {
		std::cout << "This is a Tuesday.";
	}
	if (dayOfWeek == 3) {
		std::cout << "This is a Wednesday.";
	}
	if (dayOfWeek == 4) {
		std::cout << "This is a Thursday.";
	}
	if (dayOfWeek == 5) {
		std::cout << "This is a Friday.";
	}
	if (dayOfWeek == 6) {
		std::cout << "This is a Saturday.";
	}
	if (dayOfWeek > 7) {
		
		dayOfWeekRem = dayOfWeek % 4;
		std::cout << "I DONT UNDERSTAND THIS AHHHH";
	}

}
Last edited on
sethfrias (20)
I think I solved my problems? (probably an easier way) by adding more if statements once the remainder is found.
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void returnWeekDay(int dayOfWeek, std::string weekDay, int dayOfWeekRem) {

	/*std::string weekDay;
	int dayOfWeek = int();*/

	if (dayOfWeek == 0) {
		std::cout << "This is a Sunday.\n";
	}
	if (dayOfWeek == 1) {
		std::cout << "This is a Monday.\n";
	}
	if (dayOfWeek == 2) {
		std::cout << "This is a Tuesday.\n";
	}
	if (dayOfWeek == 3) {
		std::cout << "This is a Wednesday.\n";
	}
	if (dayOfWeek == 4) {
		std::cout << "This is a Thursday.\n";
	}
	if (dayOfWeek == 5) {
		std::cout << "This is a Friday.\n";
	}
	if (dayOfWeek == 6) {
		std::cout << "This is a Saturday.\n";
	}
	if (dayOfWeek > 7) {
		
		dayOfWeekRem = dayOfWeek % 4;

		if (dayOfWeekRem == 0) {
			std::cout << "This is a Sunday.\n";
		}
		if (dayOfWeekRem == 1) {
			std::cout << "This is a Monday.\n";
		}
		if (dayOfWeekRem == 2) {
			std::cout << "This is a Tuesday.\n";
		}
		if (dayOfWeekRem == 3) {
			std::cout << "This is a Wednesday.\n";
		}
		if (dayOfWeekRem == 4) {
			std::cout << "This is a Thursday.\n";
		}
		if (dayOfWeekRem == 5) {
			std::cout << "This is a Friday.\n";
		}
		if (dayOfWeekRem == 6) {
			std::cout << "This is a Saturday.\n";
		}

		//std::cout << "I DONT UNDERSTAND THIS AHHHH";
	}

}


And I removed the declarations
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bool leapYear = isLeapYear(year);
int century = getCenturyValue(century);
int yearValue = getYearValue(yearValue);

to
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isLeapYear(year);
getCenturyValue(century);
getYearValue(yearValue);

& declared them just above

but I don't know if I should have done that...


EDIT: Changed the way the algorithm was set up to reflect correct numbers.

Still waiting on this question though just to verify my work.

Thanks!
Last edited on
Enoizat (1343)
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// Using zeller's algorithm
// F = K + ( (13 * M + 1) / 5 ) + D + (D / 4) + (C / 4) - 2 * C
// (F=Day of week), (K=Day of month), (D=Last two digits of year), 
// (C=first two digits of year(century)
#include <cmath>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>

void getInput(int&, int&, int&);
bool isLeapYear(int);
int getCenturyValue(int);
int getYearValue(int);
void displayWeekDay(int);

int main()
{
    int year = 0;
    int month = 0;
    int day = 0;
    getInput(year, month, day);
    std::cout << "This is "
              << (isLeapYear(year) ? " " : "not ")
              << "a leap year\n";

    int century = getCenturyValue(year);
    int yearValue = getYearValue(year);

    int dayOfWeek =    day + ((13 * (month + 1)) / 5) + yearValue 
                    + (yearValue / 4) + (century / 4) - (2 * century);

    displayWeekDay(dayOfWeek);
}

void getInput(int& year, int& month, int& day)
{
    std::cout << "Enter a year: ";
    std::cin >> year;
    // If M is 1 or 2, add 12 to M, and subtract 1 from Y
    std::cout << "Enter a month (1-12): ";
    std::cin >> month;
    if (month == 1 || month == 2) { month += 12; --year; }
    std::cout << "Enter a day (1-31): ";
    std::cin >> day;
    // Further controls needed: what if the user input 31 February?
}

bool isLeapYear(int year)
{
    // copied from here: http://www.cplusplus.com/forum/beginner/224391/#msg1027238
    return !(year % 4) && (year % 100 || !(year % 400));
}

int getCenturyValue(int year) { return year / 100; }

int getYearValue(int year) { return year % 100; }

void displayWeekDay(int dayOfWeek)
{
    std::vector<std::string> days { "Saturday", "Sunday",    "Monday",
                                    "Tuesday",  "Wednesday", "Thursday",
                                    "Friday" };
    std::cout << "This is a " << days.at(dayOfWeek % 7) << '\n';
}

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