双向链表

单向链表缺点分析

• 单向链表,查找的方向只能是一个方向,而双向链表可以向前或向后
• 单向链表不能自我删除,需要靠辅助节点,而双向链表可以自我删除

双向链表增删改查思路

• 遍历方式和单向链表一样,只是可以向前也可以向后查询
• 添加(默认添加到双向链表的最后)

1. 先找到双向链表的最后这个节点

2. temp.next = newHero

3. newHero.pre = temp

• 修改和单向链表一样
• 删除

1. 可以实现自我删除某个节点

2. 直接找到要删除这个节点,比如temp

3. temp.pre.next = temp.next

4. temp.next.pre = temp.pre

双向链表

class Hero {
    public Integer no;
    public String name;
    public Hero next;//后继
    public Hero pre;//前驱

    public Hero(Integer no, String name) {
        this.no = no;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Hero{" +
                "no=" + no +
                ", name='" + name + '\'' +
                '}';
    }
}

class DoubleLinked {
    private Hero head = new Hero(0, "");

    public Hero getHead() {
        return head;
    }


    //遍历双向链表
    public void list() {
        if (head.next == null) {
            System.out.println("链表为空");
            return;
        }
        Hero temp = head.next;
        while (true) {
            if (temp == null) {
                break;
            }
            System.out.println(temp);
            temp = temp.next;
        }
    }

    //顺序编号
    public void addOrder(Hero hero){
        Hero temp = head;
        while (true){
            if(temp.next == null){
                temp.next = hero;
                hero.pre = temp;
                break;
            }

            if(temp.no < hero.no && temp.next.no > hero.no){
                Hero oldTempNext = temp.next;//保存下一个节点
                oldTempNext.pre = hero;
                hero.next = oldTempNext;
                temp.next = hero;
                hero.pre = temp;
                break;
            }

            if(temp.no == hero.no){
                System.out.println("此链表有序号");
                return;
            }
            temp = temp.next;
        }
    }

    //添加
    public void add(Hero hero) {
        Hero temp = head;
        while (true) {
            /*找到链表最后为止*/
            if (temp.next == null) {
                break;
            }
            temp = temp.next;
        }
        /*形成双向链表*/
        temp.next = hero;
        hero.pre = temp;
    }

    //修改
    public void update(Hero hero) {
        Hero temp = head.next;
        boolean flag = false;
        while (true) {
            if (temp == null) {
                break;//已经遍历完
            }
            if (temp.no == hero.no) {
                flag = true;
                break;
            }
            temp = temp.next;
        }

        if (flag) {
            temp.name = hero.name;
        } else {
            System.out.println("没有找到");
        }
    }

    //删除
    public void delete(int no) {
        if (head.next == null) {
            System.out.println("队列为空");
            return;
        }
        Hero temp = head.next;

        boolean flag = false;
        while (true) {
            if (temp == null) {
                break;
            }
            if (temp.no == no) {
                flag = true;
                break;
            }
            temp = temp.next;
        }
        if (flag) {
            temp.pre.next = temp.next;
            if (temp.next != null) {
                temp.next.pre = temp.pre;
            }
        }
    }
}

public class DoubleLinkedDemo {
    public static void main(String[] args) {
        Hero x= new Hero(93, "x");
        Hero y= new Hero(33, "y");
        Hero z= new Hero(45, "z");
        DoubleLinked doubleLinked = new DoubleLinked();
        doubleLinked.addOrder(x);
        doubleLinked.addOrder(y);
        doubleLinked.addOrder(z);
        doubleLinked.list();
    }
}