509. 斐波那契数 (Swift版本)

题目

Swift Code

class Solution {
    func fib(_ n: Int) -> Int {
        let zero = 0
        let first = 1
        if n == 0 { return zero }
        if n == 1 { return first }
        return fib(n - 1) + fib(n - 2)
    }
}