go递归

1.递归的使用

package main

import (
    "fmt"
    "time"
)

func fibnum(i int) int{
    if i==0{
        return 0
    }
    if i==1{
        return 1
    }
    fmt.Println("i is",i)
    return fibnum(i-1)+fibnum(i-2)

}

func testthis(i int)  {
    if i==1{
        fmt.Println("i is 1 ,out this")
        return
    }
    if i==10{
        fmt.Println("i is 10,out this")
        return
    }
    fmt.Println("begin test; and i is now:",i)
    time.Sleep(time.Second*1)
    testthis(i-1)
    fmt.Println("when i will be print??")
    fmt.Println("i now is:",i)
    testthis(i+1)
    fmt.Println("test done, and i is now: ",i)
}


func main()  {

    fmt.Println(fibnum(3))
    testthis(5)

}

使用递归快速排序

package main

import "fmt"

func quicksort(array []int, begin, end int, mark string) {
    var i, j int
    if begin < end {
        i = begin + 1 // 将array[begin]作为基准数，因此从array[begin+1]开始与基准数比较！
        j = end       // array[end]是数组的最后一位

        for {
            if i >= j {
                break
            }
            if array[i] > array[begin] {
                array[i], array[j] = array[j], array[i]
                j = j - 1
            } else {
                i = i + 1              //此处放在else内，很重要，二分思想！
            }

        }
        //fmt.Println("array and i and j is",array,i,j)
        if array[i] >= array[begin] { 
            i = i - 1
        }

        array[begin], array[i] = array[i], array[begin]
        //fmt.Printf("%s>sort:%v\n", mark, array[begin:end])
        fmt.Println("array and i and j is",array,i,j)
        fmt.Printf("%s>%v,%d,%v\n", mark, array[begin:i], array[i], array[j:])   //后标取不到
        quicksort(array, begin, i, mark+"--")
        quicksort(array, j, end, mark+"--")
    }
}

func main() {

    nums := []int{12, 85, 25, 16, 34, 23, 49, 95, 17, 61}
    fmt.Printf("begin:%#v\n", nums)

    mark := "--"
    quicksort(nums, 0, len(nums)-1, mark)
    fmt.Printf("last:%#v\n", nums)
}

2.关于递归上下文的测试

package main

import (
    "fmt"
)


var i int = 0


func testagain(step int){

    if step==5{
        //fmt.Println(a)
        return
    }
    fmt.Println("begin i is:",i)
    i++
    testagain(step+1)
    fmt.Println("after i is",i)
    i--
    return

}
func main(){
    testagain(1)
}

运行的结果如下：

begin i is: 0
begin i is: 1
begin i is: 2
begin i is: 3
after i is 4
after i is 3
after i is 2
after i is 1