JAVA双向链表

JAVA双向链表操作

双向链表的每一个结点都有一条指向其后继结点的next指针和一条指向其前结点的pre指针。
双向链表的插入图示：

双向链表的删除图示：

import java.io.IOException;
import java.util.Scanner;

class Node{
    public int data;//数据域
    public Node next;//后继指针域
    public Node previous;//前驱指针域

    public Node(int data) {
        this.data = data;
        this.next = null;
        this.previous = null;
    }
    //显示该结点的数据
    public void display() {
        System.out.print( data + " ");
    }
}

public class Main {

    public static Node head = null;//表头
    public static int length = 0;

    //在链表头部添加结点
    public static void addHead(int data) {
        Node newNode = new Node(data);
        if(head == null) {
            head = newNode;//如果链表为空，增加新结点
        }
        else {
            newNode.next = head;
            head.previous = newNode;
            head = newNode;
        }
        length++;
    }

    //在链表头部删除结点
    public static void deleteHead() {
        if(head == null){
            System.out.println("空表，删除的结点不存在");
        }
        else {
            Node curNode = head;
            head = curNode.next;
            head.previous = null;
        }
        length--;
    }

    //在链表尾部添加结点
    public static void addTail(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node curNode = head;
            int count = 1;
            while (count < length) {
                curNode = curNode.next;
                count++;
            }
            newNode.next = null;
            newNode.previous = curNode;
            curNode.next = newNode;
        }
        length++;
    }

    //在链表尾部删除结点
    public static void deleteTail() {
        if(head == null){
            System.out.println("空表，删除的结点不存在");
        }else{
            Node preNode = head;
            int count = 1;
            while(count < length-1) {
                preNode = preNode.next;
                count++;
            }
            preNode.next = null;
        }
        length--;
    }


    //正向遍历链表
    public static void printOrderNode() {
        if(head == null) {
            System.out.println("空表");
        }
        Node curNode = head;
        while (curNode != null) {
            curNode.display();
            curNode = curNode.next;
        }
        System.out.println();
    }

    //反向遍历链表
    public static void printReverseNode() {
        if(head == null) {
            System.out.println("空表");
        }
        Node curNode = head;
        while (curNode.next != null) {
            curNode = curNode.next;
        }
        while (curNode != null) {
            curNode.display();
            curNode = curNode.previous;
        }
        System.out.println();
    }

    //在指定位置插入结点
    public static void insertList(int data, int index) {
        Node newNode = new Node(data);
        if(head == null){
            head = newNode;//链表为空，插入
        }
        if(index > length+1 || index < 1) {
            System.out.println("结点插入的位置不存在，可插入的位置为1到"+(length+1));
        }
        if(index == 1) {
            newNode.next = head;
            head.previous = newNode;
            head = newNode;//在链表开头插入
        } else{              //在链表中间或尾部插入
            Node preNode = head;
            int count = 1;
            while(count < index-1) {
                preNode = preNode.next;
                count++;
            }
            Node curNode = preNode.next;
            newNode.next = curNode;
            newNode.previous = preNode;
            preNode.next = newNode;
            if(curNode != null) {
                curNode.previous = newNode;
            }
        }
        length++;
    }

    //在指定位置删除结点
    public static void deleteList(int index) {
        if(index > length || index < 1) {
            System.out.println("结点删除的位置不存在，可删除的位置为1到"+length);
        }
        if(index == 1) {
            Node curNode = head;
            head = curNode.next;
            head.previous = null;
            length--;
        } else{
            Node preNode = head;
            int count = 1;
            while(count < index-1) {
                preNode = preNode.next;
                count++;
            }
            Node curNode = preNode.next;
            Node laterNode = curNode.next;
            preNode.next = laterNode;
            if(laterNode != null) {  //若被删除结点的后继结点不是null结点，那么设置其前驱结点
                laterNode.previous = preNode;//指针指向被删除结点的前驱结点
            }
            length--;
        }
    }

    //查找数据是否存在,与单链表一样
    public static boolean containData(int data) {
        if(head == null){
            System.out.println("空表");
            return false;
        }
        Node curNode = head;
        while(curNode.data!= data){
            if(curNode.next == null) {
                System.out.println("结点数据不存在");
                return false;
            }
            curNode =curNode.next;
        }
        System.out.println("结点数据存在");
        return true;
    }

    //获取指定位置的数据，与单链表一样
    public static void getIndexData(int index) {
        if(head == null){
            System.out.println("空表");
        }
        if(index > length || index < 1) {
            System.out.println("结点位置不存在，可获取的位置为1到"+length);
        }
        Node curNode = head;
        int count =1;
        while(count != index) {
            curNode =curNode.next;
            count++;
        }
        curNode.display();
        System.out.println();
    }

    //修改指定位置的结点数据，与单链表一样
    public static void updateIndexData(int index, int data) {
        if(head == null){
            System.out.println("空表");
        }
        if(index > length || index < 1) {
            System.out.println("结点位置不存在，可更新的位置为1到"+length);
        }
        Node curNode = head;
        int count =1;//while也可以用for循环方式解决
        while(count != index) {
            curNode =curNode.next;
            count++;
        }
        curNode.data = data;
    }

    //打印链表
    public static void printList(){
        Node tmp = head;
        while(tmp != null){
            System.out.print(tmp.data + " ");
            tmp = tmp.next;
        }
        System.out.println();
    }

    public static void main(String []args) throws IOException {
        Scanner sc = new Scanner(System.in);
        while (true) {
            int s = sc.nextInt();
            if(s == 0) {
                break;
            }else {
                addHead(s);
            }
        }
        //输入样例
        //1
        //2
        //3
        //0 输入0结束
        printList();
        deleteHead();
        printList();
        printOrderNode();

        Scanner in = new Scanner(System.in);
        int index = sc.nextInt();
        int data = sc.nextInt();
        insertList(data, index);
        printList();
    }
}