golang实现Fibonacii的几种算法

package fib

/**
Fibonacii的几种算法实现
*/

// 直接循环计算
func Fib(n int) int {
f := [3]int{0, 1, 1}
if n < 0 {
return -1
}

if n < 3 {
return f

}

for i := 3; i <= n; i++ {
f[0], f[1] = f[1], f[2]
f[2] = f[0] + f[1]
}

return f[2]
}

// 略微修改，没有任何数据中间交换哦~~
func Fib2(n int) int {
f := [2]int{0, 1}
if n < 0 {
return -1
}

if n < 2 {
return f

}

for i := 2; i <= n; i++ {
f[i&1] += f[(i+1)&1]
}

return f[n&1]
}

//递归算法，效率低
func FibRec(n int) int {
if n < 0 {
return -1
}
return fib_recursion(n)
}

func fib_recursion(n int) int {
if n < 3 {
return 1
}
return fib_recursion(n-1) + fib_recursion(n-2)
}

//尾递归算法
func FibTail(n int) int {
if n < 0 {
return -1
}

if n < 3 {
return 1
}

return fib_tail_recursion(n, 1, 1, 3)
}

func fib_tail_recursion(n int, a int, b int, begin int) int {
if n == begin {
return a + b
}
return fib_tail_recursion(n, b, a+b, begin+1)
}

package fib

import (
//"fmt"
"testing"
)

func TestFib(t *testing.T) {
n := 10
f := Fib(n)
if f != 55 {
t.Error("Fib() failed. Got", f, "Expected 55 ")
}
}

func TestFib2(t *testing.T) {
n := 10
f := Fib2(n)
if f != 55 {
t.Error("Fib2() failed. Got", f, "Expected 55 ")
}
}

func TestFibRec(t *testing.T) {
n := 10
f := FibRec(n)
if f != 55 {
t.Error("FibRec() failed. Got", f, "Expected 55 ")
}
}

func TestFibTail(t *testing.T) {
n := 10
f := FibTail(n)
if f != 55 {
t.Error("FibTail() failed. Got", f, "Expected 55")
}
}

func BenchmarkFib(b *testing.B) {
for i := 0; i < b.N; i++ {
Fib(1000)
}
}

func BenchmarkFib2(b *testing.B) {
for i := 0; i < b.N; i++ {
Fib2(1000)
}
}

func BenchmarkFibTail(b *testing.B) {
for i := 0; i < b.N; i++ {
FibTail(1000)
}
}