Leap Year Program Help

[Kendawg]

Hello, I've been having some trouble for my class assignment. I'm supposed to input a year and then it will output if the year is a leap-year or not.

A year with 366 days is called a leap year.

A year is a leap year if it is divisible by four (for example, 1980), except that it is not a leap year if it is divisible by 100 (for example, 1900); however, it is a leap year if it is divisible by 400 (for example, 2000).

There were no exceptions before the introduction of the Gregorian calendar on October 15, 1582 (1500 was a leap year).

Write a program that asks the user for a year and computes whether that year is a leap year.

Here is my code so far.

#include <iostream>

using namespace std;

int main()
{
	int number;
	cout << "Enter a year. " << endl;
	cin >> number;

	if (number % 4 == 0)
	{
		if (number % 100 != 0)
		{
			if (number % 400 == 0)
			{
				cout << "The year is a leap year." << endl;
			}
		}
	}
	else
	{
		cout << "The year isn't a leap year." << endl;
	}
	
	return 0;
}

I'm just not sure where I went wrong here.. I'm not asking anyone to do my homework here, just some help in the right direction would be appreciated.

Thanks!

[vlad from moscow]

These conditions

if (number % 100 != 0)
{
if (number % 400 == 0)
{
contradict each other. That is if number % 100 != 0 then it is not a value that is divisible by 400. Also you have not enough ellse statements that to print messages that a year is not leap.

[freddy92]

You don't want to nest the last if you have there, it should be part of an if...else if statement, like this:

if(number % 4 == 0)
{
    if (number % 400 == 0)
         // leap year
    else if (number % 100 == 0)
        // not a leap year
    else 
        //leap year
}

There's probably a better way to do this but this should put you on the right track.

[vlad from moscow]

@freddy92
You don't want to nest the last if you have there, it should be part of an if...else if statement, like this:

if(number % 4 == 0)
{
    if (number % 400 == 0)
         // leap year
    else if (number % 100 == 0)
        // not a leap year
    else 
        //leap year
} 

I would rewrite your code snip the following way

if ( number % 400 == 0 )
         // leap year
else if ( number % 100 == 0 )
        // not a leap year
else if ( number % 4 == 0 ) 
        //leap year
else
        // not a leap year 

But in any case it is more simply to write

if ( number % 4 == 0 && ( number % 100 != 0 || number % 400 == 0 ) )
{
   cout << "The year is a leap year." << endl;
}
else
{
   cout << "The year isn't a leap year." << endl;
}

Or even the following way

auto IsLeap = []( int year ) 
{ 
   return ( year % 4 == 0 && ( year % 100 != 0 || year % 400 == 0 ) );
};

cout << "The year is " << ( IsLeap( number ) ? "" : "not " ) << "a leap year." << endl;

[Kendawg]

Thanks guys so much for the help. I'm positive I can rewrite the code the right way now!