Go斐波拉契数列(Fibonacci)(多种写法)

//recursion
func fib(n int) int{
	if n < 2{
		return n
	}else{
		return fib(n-1) + fib(n-2)
	}

}

func fibcore(n int) (int,int){
	if n < 2{
		return 0,n
	}else{
		a,b := fibcore(n-1)
		return b,a+b
	}

}

//tail recursion
func fib2(n int)(int){
	_,b:= fibcore(n)
	return b
}

//iteration 
func fib3(max int)(int){
	n:=0
	a,b:=0,1
	for {
		if n < max{
			a,b = b,a+b
			n ++
		}else{
			break
		}
	}
	return b
}