package main

import (
    "strings"
    "strconv"
    "fmt"
)

/**
    雙向鏈表
 */
type DoubleLinkedList struct {
    //鏈表頭節(jié)點
    head *Node
    //鏈表尾部節(jié)點
    tail *Node
    //長度
    size int

}
/**
    遍歷器接口
 */
type Interater interface{
    /**
        是否還有下一個
     */
    hasNext() bool
    /**
        下一個節(jié)點
    */
    next() *Node

}
/**
    遍歷器
 */
type ListInterater struct {
    list *DoubleLinkedList
    currentNode *Node
}
/**
    遍歷器是否還有下一個節(jié)點
 */
func (inter *ListInterater) hasNext() bool{
    if inter.currentNode==nil && inter.list.head!=nil {
        return true
    }else if  inter.currentNode==nil && inter.list.head==nil {
        return false
    }else{
        return inter.currentNode.next!=nil
    }

}
/**
    遍歷器獲取下一個節(jié)點
 */
func (inter *ListInterater) next() *Node{
    if inter.currentNode==nil && inter.list.head!=nil{
        inter.currentNode = inter.list.head
    }else if(inter.currentNode==nil && inter.list.head==nil){
        return nil
    }else{
        inter.currentNode = inter.currentNode.next
    }
    return inter.currentNode
}

/**
    節(jié)點
 */
type Node struct {
    data interface{}
    prev *Node
    next *Node

}

func (list *DoubleLinkedList) GetHead() *Node  {
    return list.head
}

func (list *DoubleLinkedList) GetTail() *Node  {
    return list.tail
}

func (list *DoubleLinkedList) Size() int  {
    return list.size
}

func (list *DoubleLinkedList) initFromNode(node *Node)  {
    list.head = node
    list.tail = node
    list.size = 1
}

func (list *DoubleLinkedList) addHead(node *Node){
    oldHead :=list.head
    oldHead.prev = node
    node.next = oldHead
    node.prev = nil
    list.head = node
    list.size++
}
/**
    獲取鏈表的遍歷器
 */
func (list *DoubleLinkedList) Iterater() *ListInterater{
    inter:=ListInterater{
        list:list,
        currentNode:nil,
    }
    return &inter
}
/**
    從頭部添加節(jié)點
 */
func (list *DoubleLinkedList) AddFromHead(node *Node) {
    if list.head==nil && list.tail==nil {
        list.initFromNode(node)
    }else{
        list.addHead(node)
    }
}
/**
    從尾部添加節(jié)點
 */
func (list *DoubleLinkedList) addTail(node *Node){
    oldTail :=list.tail
    oldTail.next = node
    node.prev = oldTail
    node.next = nil
    list.tail = node
    list.size++
}
/**
    刪除指定位置節(jié)點
 */
func (list *DoubleLinkedList) Remove(index int) {
    node:=list.Get(index)
    if node==nil {
        return
    }
    prev:=node.prev
    next:=node.next
    if prev!=nil {
        prev.next=next
    }
    if next!=nil {
        next.prev=prev
    }
    list.size--
}

/**
    從后面追加節(jié)點
 */
func (list *DoubleLinkedList) Append(node *Node) {
    if list.head==nil && list.tail==nil {
        list.initFromNode(node)
    }else{
        list.addTail(node)
    }
}
/**
    獲取指定位置節(jié)點
 */
func (list *DoubleLinkedList) Get(index int) *Node {
    next:=list.head
    for i:=0;i