Fibonacci bottom-up optimised

Fibonaccibottomupoptimised

func fib (_ num: Int) -> Int {
    guard num > 1 else { return num }
    var a = 0
    var b = 1
    var c = 0
    for _ in 2..<num {
        c = a + b
        a = b
        b = c
    }
    return a + b
}