// List represents a doubly linked list.
// The zero value for List is an empty list ready to use.
type List struct {
    root Element // sentinel list element, only &root, root.prev, and root.next are used
    len  int     // current list length excluding (this) sentinel element
}

  // Element is an element of a linked list.
  type Element struct {
      // Next and previous pointers in the doubly-linked list of elements.
      // To simplify the implementation, internally a list l is implemented
      // as a ring, such that &l.root is both the next element of the last
      // list element (l.Back()) and the previous element of the first list
      // element (l.Front()).
      next, prev *Element

      // The list to which this element belongs.
      list *List

      // The value stored with this element.
      Value interface{}
  }

    mylist := list.New()
    fmt.Println(mylist)       //输出list中内容
    fmt.Println(mylist.Len()) //查看链表中元素的个数
    fmt.Printf("%p", mylist)  //输出地址

    //添加到最后,List["a"]
    mylist.PushBack("a")
    //添加到最前面,List["b","a"]
    mylist.PushFront("b") 
    //向第一个元素后面添加元素,List["b","c","a"]
    mylist.InsertAfter("c", mylist.Front()) 
    //向最后一个元素前面添加元素,List["b","c","d","a"]
    mylist.InsertBefore("d", mylist.Back()) 

    fmt.Println(mylist.Back().Value)  //最后一个元素的值
    fmt.Println(mylist.Front().Value) //第一个元素的值

    //只能从头向后找,或从后往前找,获取元素内容
    n := 5
    var curr *list.Element
    if n > 0 && n <= mylist.Len() {
        if n == 1 {
            curr = mylist.Front()
        } else if n == mylist.Len() {
            curr = mylist.Back()
        } else {
            curr = mylist.Front()
            for i := 1; i < n; i++ {
                curr = curr.Next()
            }
        }
    } else {
        fmt.Println("n的数值不对")
    }
    //遍历所有值
    for e := mylist.Front(); e != nil; e = e.Next() {
        fmt.Println(e.Value)
    }

    mylist.MoveToBack(mylist.Front()) //把第一个移动到后面
    mylist.MoveToFront(mylist.Back()) //把最后一个移动到前面
    mylist.MoveAfter(mylist.Front(),mylist.Back())//把第一个参数元素,移动到第二个参数元素后面
    mylist.MoveBefore(mylist.Front(),mylist.Back())//把第一个参数元素,移动到第二个参数元素前面

mylist.Remove(mylist.Front())

// A Ring is an element of a circular list, or ring.
// Rings do not have a beginning or end; a pointer to any ring element
// serves as reference to the entire ring. Empty rings are represented
// as nil Ring pointers. The zero value for a Ring is a one-element
// ring with a nil Value.
//
type Ring struct {
    next, prev *Ring
    Value      interface{} // for use by client; untouched by this library
}

    type Ring
        //实例化长度为n的环形链表
        func New(n int) *Ring
        //长度
        func (r *Ring) Len() int
        //下一个元素
        func (r *Ring) Next() *Ring
        //上一个元素
        func (r *Ring) Prev() *Ring
        //移动n次,支持负数
        func (r *Ring) Move(n int) *Ring
        //合并s和r
        func (r *Ring) Link(s *Ring) *Ring
        //删除r后面n%r.Len()元素,删除多个,当前元素前面的不删除
        func (r *Ring) Unlink(n int) *Ring
        //循环遍历,i是当前元素的值
        func (r *Ring) Do(f func(interface{}))

    r := ring.New(3)
    for i := 0; i < r.Len(); i++ {
        r.Move(i).Value = i
    }
    r.Do(func(i interface{}) {
        fmt.Println(i)
    })

    fmt.Println(r.Next().Value)//输出:1
    fmt.Println(r.Next().Next().Value)//输出:2
    fmt.Println(r.Next().Next().Next().Value)//输出:0
    fmt.Println(r.Move(-1).Value)//输出:2
    fmt.Println(r.Prev().Value)//输出:2

    s := ring.New(1)
    s.Value = 13
    //r是哪个元素,就把新的链表添加到哪个元素后面
    r.Link(s)
    r.Do(func(i interface{}) {
        fmt.Print(i, " ")
    })
    fmt.Println("")
    //从r元素向后,n/r.Len()个元素被删除,当前元素和前面的保留
    r.Unlink(1)
    r.Do(func(i interface{}) {
        fmt.Print(i, " ")
    })