That guard is really confusing. It reads like "if array is not 'not empty' then return nil. isEmtpy is better than count == 1 but I think guard should be reserved for failing to bind an optional value at the beginning of the function.

I like the use of isEmpty, but agree that guard makes it more confusing than it needs to be. So I'll close this PR and make those changes.

Why not simply...

if array.isEmpty { return nil }
return array.removeLast()

I don't think an else is necessary here.

The else is not strictly necessary, but in my opinion it does clarify the flow of what's going on.

In that case, what about ...

return array.isEmpty ? nil : array.removeLast()

😄

Perfectly fine, but since the goal of this project is to teach algorithms I'd prefer to stick with an simple if-else since everyone understands that.