golang 的双向循环链表

         如下为go 实现的双向循环列表。

package main

import (
           "fmt"
       ) 
       
       
type Ring struct{
    prev, next *Ring
    val interface{}
}       


func (r *Ring)init() *Ring {
   r.prev = r
   r.next = r   
   return r
}


func (r *Ring)iterate_clockward(){
    cur := r.next
   
    if cur == r {
       fmt.Println("clockward sigle node ")
       return
    }
   
    for cur != r {
       
       fmt.Println("cur ", cur.val)
       cur = cur.next
    }
}


func (r *Ring)iterate_counterclock(){

    cur := r.prev
    if cur == r {
       fmt.Println("counterclock sigle node")
       return
    }
   
    for cur != r {
       fmt.Println("cur ", cur.val)
       cur = cur.prev
    }
}


//insert in the first place, r as the head
func (r *Ring)insert(a interface{}){
    
    node := new(Ring)     
    node.val = a
    
    next := r.next
    
    node.next = next
    node.prev = r
    
    r.next = node
    next.prev = node    
}


func (r *Ring)unlink(a interface{}){
   
   cur := r.next
   
   if cur == r {
      fmt.Println("single node")
      return
   }
   
   for cur != r {
       if cur.val == a {
          prev := cur.prev
          next := cur.next
          prev.next = next
          next.prev = prev
          return
       }
       
       cur = cur.next
   }
}


func (r *Ring)len() int {
   
   cur := r.next
   
   if cur == r {
      fmt.Println("single node")
      return 0
   }
   
   i := 0
   for cur != r {
       i++       
       cur = cur.next
   }
   
   return i
}


func main(){

   r := new(Ring)
   r.init()
   
   for i := 0; i < 5; i++ {
       r.insert(i)
   }
   
   r.iterate_clockward()
   
   fmt.Println("before unlink len", r.len())
   
   r.unlink(2)
   
   fmt.Println("after unlink len", r.len())     
   
   fmt.Println("counter clock")
   
   r.iterate_counterclock()

}

打印结果如下:

cur 4
cur 3
cur 2
cur 1
cur 0
before unlink len 5
after unlink len 4
counter clock
cur 0
cur 1
cur 3
cur 4