Leap Year Exercise in Lesson 11 (Making Decisions.Playground)

let aYear = 1700 // change year here to test the function
 
func isLeap (year: Int){
   
  if (aYear % 4 == 0 && aYear % 100 == 0 && aYear % 400 == 0) || (aYear % 4 == 0 && aYear % 100 != 0){
    print("YES")
  } else {
    print("NO")
  }
}

isLeap(year: aYear) //function call

---

This seemed the most straightforward way to solve it.

A year is a leap year in two cases.
Case 1: The year equally divided by 4 AND equally divided by 100 AND while equally divided by 400.
OR
Case 2: The year is equally divided by 4 AND is NOT equally divided by 100.

func isLeapYear(_ year: Int) -> Bool {

    if number(year, isDivisibleBy: 4)==false {

        return false

    }

    else if number(year, isDivisibleBy: 100)==false {

        return true

    }

    else if number(year, isDivisibleBy: 400){

        return true

    }

    else {return false}}

Here is my solution; I don't know if it can be done in an easier way but this is how I did it and it works:

func isLeap(year: Int) {

    if year % 4 == 0 && year % 100 != 0 && year % 400 == 0 {

        print("YES")

    } else if year % 4 == 0 && year % 400 == 0 {

        print("YES")

    } else if year % 4 == 0 && year % 100 != 0 {

        print("YES")

    } else if year % 100 == 0 {

        print("NO")

    } else {

        print("NO")

    }

}

isLeap(year: 2000) // write here whatever number you want

This also works fine:

I came up with the following logic, which works and is quite simple:

let aYear =  1300

func isLeap() {

if aYear % 400 == 0 {  
print("YES")

} else if aYear % 4 == 0 && aYear % 100 != 0 {

print("YES")

 } else {  
print("NO")

}

}

isLeap()

Two simple ways to solve this exercise:

1. Using build-in method "isDivisableBy":

    if number(year, isDivisibleBy: 400 ) {
        return true
    }
    else if number(year, isDivisibleBy: 100 ){
        return false
    }
    else if number(year, isDivisibleBy: 4 ){
        return true
    } else {
    return false
    }
}

1. Less elegant, defining three constants:

let isDivisableBy4 = 0
let isDivisableBy100 = 0
let isDivisableBy400 = 0

    if year%400 == isDivisableBy400 {
        return true
    }
        else if year%100 == isDivisableBy100 {
            return false
        }
            else if year%4 == isDivisableBy4 {
                return true
            }
                else {
                    return false
                }
            }

As you can see, the key is in proper order.