数据结构-链表带哨兵

一.链表带哨兵

import java.util.Iterator;
import java.util.function.Consumer;
//带哨兵
public class shuju02 implements Iterable<Integer> {//整体
    private Node head=new Node(666,null);//头指针

​    @Override
​    public Iterator<Integer> iterator() {
​        //匿名内部类->带名字的内部类
​        return new NodeIterator();
​    }
​    private class NodeIterator implements Iterator<Integer> {
​        Node p=head.next;

​        @Override
​        public boolean hasNext() {//是否有下一个元素
​            return p!=null;//不空返回真
​        }

​        @Override
​        public Integer next() {//返回当前值,并指向下一个元素
​            int v=p.value;
​            p=p.next;
​            return v;
​        }
​    }

​    private static class Node {
​        int value;//值
​        Node next;//下一个节点指针

​        public Node(int value, Node next) {
​            this.value = value;
​            this.next = next;
​        }
​    }

​    public void addFirst(int value) throws IllegalAccessException {
​        //1.链表为空
​        // head=new Node(value,null);
​        //2.链表非空(头插)
​       /* head = new Node(value, head);*/
​        insert(0,value);
​    }

​    //遍历链表
​    //Params:consumer-要执行的操作
​    public void loop(Consumer<Integer> consumer) {
​        Node p = head;
​        while (p != null) {
​            consumer.accept(p.value);
​            p = p.next;
​        }
​    }
​    //遍历链表2
​    //Params:consumer-要执行的操作
​    public void loop2(Consumer<Integer> consumer) {
​        for (Node p = head; p != null; p = p.next){
​            consumer.accept(p.value);
​        }
​    }
​    //遍历链表3(递归遍历)
​    //Params:consumer-要执行的操作
​    public void loop3(Consumer<Integer>before,//没有哨兵
​                      Consumer<Integer>after){
​        recursion(head,before,after);
​    }
​    private void recursion(Node curr,//当前节点
​                           Consumer<Integer>before,Consumer<Integer>after){//某个节点要进行的操作
​        if(curr==null){
​            return;
​        }
​        before.accept(curr.value);
​        recursion(curr.next,before,after);//放前边倒叙,放后面顺序->指这句话
​        after.accept(curr.value);
​    }

​    private Node findLast(){
​        Node p;
​        for(p=head;p.next!=null;p=p.next){

​        }
​        return p;
​    }
​    public void addLast(int value){
​        Node last=findLast();
​        last.next=new Node(value,null);
​    }
  /* public void test(){
​        int i=0;
​        for(Node p=head;p!=null;p=p.next,i++){
​            System.out.println(p.value+"索引是:"+i);
​        }
​        根据索引查找
Params:index-索引
Returns:找到，返回该索引位置节点的值
Throws:IlLegalArgumentException-找不到，抛出index非法异常
   }*/

​    private Node findNode(int index){//给定索引位置
​        int i=-1;
​        for(Node p=head ;p!=null;p=p.next,i++){
​            if(i==index){
​                return p;
​            }
​        }
​        return null;//没找到
​    }
​    public int get(int index) throws IllegalAccessException {
​        Node node=findNode(index);
​        if(node==null){
​            //抛异常
​            illegalIndex(index);
​        }
​        return node.value;
​    }
​    //异常处理(重点)
​    private static void illegalIndex(int index) throws IllegalAccessException {
​        throw new IllegalAccessException(
​                String.format("index[%d] 不合法%n", index)
​        );
​    }


​    /*
向索引位置插入
 */
​    public void insert(int index,int value) throws IllegalAccessException {
​        Node prev=findNode(index-1);//找到上一个节点
​        if(prev==null){
​            illegalIndex(index);
​        }
​        prev.next=new Node(value,prev.next);

​    }
​    //1.问题
​    //删除头节点
​    public void removeFirst() throws IllegalAccessException {
​     remove(0);
​    }
​    public void remove(int index) throws IllegalAccessException {
​        Node prev=findNode(index-1);//上一个节点
​        if(prev==null){
​            illegalIndex(index);
​        }
​        Node removed=prev.next;//被删除的节点
​        if(removed==null){
​            illegalIndex(index);
​        }
​        prev.next=removed.next;

​    }
}

二.双向链表带哨兵

import java.util.Iterator;

//双向链表,带哨兵
public class shuju03 implements Iterable<Integer>{
static class Node{
    Node prev;//上一个节点指针
    int value;
    Node next;//下一个节点指针

    public Node(Node prev, int value, Node next) {
        this.prev = prev;
        this.value = value;
        this.next = next;
    }
}
private Node head;//头哨兵
private Node tail;//尾哨兵

    public shuju03(){
        head=new Node(null,666,null);
        tail=new Node(null,666,null);
       head.next=tail;
       tail.prev=head;
    }

    private Node findNode(int index){
        int i=-1;
        for(Node p=head;p!=tail;p=p.next,i++){
            if(i==index){
                return p;
            }
        }
        return null;
    }

    public void addFirst(int value) throws IllegalAccessException {
        insert(0,value);
    }
    public void removeLast() throws IllegalAccessException {
        Node removed=tail.prev;
        if(removed==head){
            illegalIndex(0);
        }
        Node prev=removed.prev;
        prev.next=tail;
        tail.prev=prev;
    }


    public void addLast(int value){
     Node last=tail.prev;
     Node added=new Node(last,value,tail);
     last.next=added;
     tail.prev=added;
    }

    public void insert(int index,int value) throws IllegalAccessException {
        Node prev=findNode(index-1);
        if(prev==null){
           illegalIndex(index);
        }
        Node next=prev.next;
        Node inserted=new Node(prev,value,next);
        prev.next=inserted;
        next.prev=inserted;
    }

    public void remove(int index) throws IllegalAccessException {
        Node prev=findNode(index-1);
        if(prev==null){
            illegalIndex(index);
        }
        Node removed=prev.next;
        if(removed==tail){
            illegalIndex(index);
        }
        Node next=removed.next;

       prev.next=next;
       next.prev=prev;

    }
    private static void illegalIndex(int index) throws IllegalAccessException {
        throw new IllegalAccessException(
                String.format("index[%d] 不合法%n", index)
        );
    }
    @Override
    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {
            Node p=head.next;
            @Override
            public boolean hasNext() {
                return p!=tail;
            }

            @Override
            public Integer next() {
                int value=p.value;
                return value;
            }
        };
    }
}

三.双向链表

import java.util.Iterator;

public class shuju04 implements Iterable<Integer> {
    @Override
    public Iterator<Integer> iterator() {
        return new Iterator<Integer>() {
            Node p=sentinel.next;
            @Override
            public boolean hasNext() {
                return p!=sentinel;
            }

            @Override
            public Integer next() {
                int value= p.value;
                p=p.next;
                return value;
            }
        };
    }

    /*
           s->1->2->3->1->s
             */
    private static class Node{
        Node prev;
        int value;
        Node next;

            public Node(Node prev, int value, Node next) {
                this.prev = prev;
                this.value = value;
                this.next = next;
            }
        }
        private Node sentinel=new Node(null,-1,null);

        public shuju04(){
            sentinel.prev=sentinel;
            sentinel.next=sentinel;
        }
        //添加到第一个
    //Params value-待添加值
    public void addFirst(int value){
      Node a=sentinel;
      Node b=sentinel.next;
      Node added=new Node(a,value,b);
      a.next=added;
      b.prev=added;
    }
    //添加到最后一个
    //Params:value-待添加值
    public void addLast(int value){
           Node a=sentinel.prev;
           Node b=sentinel;
           Node added=new Node(a,value,b);
           a.next=added;
           b.prev=added;
    }
    //删除第一个
    public void removeFirst() {
            Node removed=sentinel.next;
            if(removed==sentinel){
                throw new IllegalArgumentException("非法");
            }
            Node a=sentinel;
            Node b=removed.next;
            a.next=b;
            b.prev=a;
    }
    //删除最后一个
    public void removeLast(){
            Node removed=sentinel.prev;
            if(removed==sentinel){
                throw  new IllegalArgumentException("非法");
            }
            Node a=removed.prev;
            Node b=sentinel;

            a.next=b;
            b.prev=a;
    }
  //根据值删除
   // Params:value-目标值
    public void removeByValue(int value){
      Node removed=findByValue(value);
      if(removed==null){
          return;//不用删
      }
      Node a=removed.prev;
      Node b=removed.next;
      a.next=b;
      b.prev=a;
    }
    private Node findByValue(int value){
           Node p=sentinel.next;
           while(p!=sentinel){
               if(p.value==value){
                   return p;
               }
               p=p.next;
           }
           return null;
    }



}

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