Collatz function

Collatz+.playground

// Returns the number of iterations to get from n to 1
// when following the sequence that forms the basis of the 
// Collatz conjecture (https://en.wikipedia.org/wiki/Collatz_conjecture)
func collatz(_ n : Int) -> Int {
	if n  == 1 {
		// end at 1
		return 0
	}
	else if n % 2 == 0 {
		// even
		return 1 + collatz(n / 2)
	}
	else {
		// odd
		return 1 + collatz(3 * n + 1)
	}
}

collatz(1)

collatz(3000)

collatz(63_728_127)

collatz(999_999_999_999)

Why the "1+" on the return? Shouldn't it just be collatz(n/2) and collatz(3*n+1)?

@mjcohen Both versions add 1 every time collatz() is called. Look carefully at how this version differs from the original, in terms of where this addition is done.

@mjcohen The "1+" is because there is no longer a count variable that increments every time collatz is called.

What's probably unclear from the implementation is that the return value is the number of iterations. I should have made the function name more explicit about it, maybe.