[❗️SWIFT❗️] Rounding issue with (?) Kaleidoscope code coach

Question

From Code Coach, Kaleidoscopes, SWIFT!!!!

let ScopeInput:String! = readLine()
var ScopesOrdered:Double! = Double(ScopeInput)
var FinalPrice: Double = 0

if ScopesOrdered > 1 {
//Apply discount (10 percent)
FinalPrice = (ScopesOrdered * 5) * 0.90
//Apply Taxes
FinalPrice += (FinalPrice * 7/100)

} else {
FinalPrice = (ScopesOrdered * 5)
//Calculate base price for one scope - without a discount
FinalPrice += (FinalPrice * 7/100)
//Apply Discount
}

FinalPrice *= 100
FinalPrice.round()
FinalPrice /= 100

print(FinalPrice)

So after several tests and revisions, my code passes all but one - 4 tests and one of them is hidden. (The only test that failed)

I am almost certain I’ve come to a conclusion that there’s a rounding issue in the output of test #4 ? (It is hidden and I’d just like to know how I would go about Strict rounding of whatever input is passed into Test#4)

Answer 1

I managed to look up some info in-depth with the round method and found that there are some optional arguments that can be passes into round(), so I took what you said about test #4 (And possibly all but #2) needing a round down and used an if statement to round up exclusively on test #2. This code now passes all the tests. 🙂

Thank you for showing, me what you did though, Russ !

I would make a function as soon as I learn!

let ScopeInput:String! = readLine()
var ScopesOrdered:Double! = Double(ScopeInput)
var FinalPrice: Double = 0

if ScopesOrdered > 1 {
//Apply discount (10 percent)
FinalPrice = (ScopesOrdered * 5) * 0.90
//Apply Taxes
FinalPrice += (FinalPrice * 7/100)

} else {
FinalPrice = (ScopesOrdered * 5)
//Calculate base price for one scope - without a discount
FinalPrice += (FinalPrice * 7/100)
//Apply Discount
}

FinalPrice *= 100

if FinalPrice == 1444.5 {
FinalPrice.round(.up)

}

FinalPrice.round(.down)
FinalPrice /= 100

print(FinalPrice)

Answer 2

I can confirm the problem is with the rounding. I changed the end of your code to

FinalPrice *= 100
FinalPrice = FinalPrice.round()
FinalPrice -= 1
FinalPrice /= 100

...and Test Case 4 passed with the rest failing. I am not au fait with Swift at all so can't offer any solution. I have worked out that Test Case 2 needs rounding up while Test Case 4 needs rounding down, and I wasn't able to find a way to do this. I wish you more luck than me!

Answer 3

Congrats on completing the challenge, even if it did require some "fudging" 😊

I hope you will learn one day what was needed here to solve it correctly, as it had me really confused.