Check a +ve Int is 2^n where n is non -ve Int

check.swift

//Check a +ve Int is 2^n where n is non -ve Int

func check(_ i: Int) -> Bool {
    guard i != 1 else { return true }
    guard i % 2 == 0 else { return false }
    return check(i / 2)
}

print(check(1024))
print(check(1023))

/*
for i in (0...1024) {
    print("\(i) is \(check(i))")
}
*/

func check2(_ i: Int) -> Bool {
    return String(i, radix: 2).filter({ $0 == "1" }).count == 1
}

print(check2(1024))
print(check2(1023))