单链表代码

/**
 * Created with Intellij IDEA
 * ClassName:MyLinkedList
 * User:MaLe
 * Description:单链表
 * @Date:2021/10/23
 * @Time:9:40
 * @author:395645313@qq.com
 */
class Node {
    public int val;//0
    public Node next;//null

    public Node(int val) {
        this.val = val;
    }
}

public class MyLinkedList {

    public Node head;//单链表的头节点的引用


    public void createLinkedList() {
        Node node1 = new Node(12);
        Node node2 = new Node(23);
        Node node3 = new Node(34);
        Node node4 = new Node(45);
        node1.next = node2;
        node2.next = node3;
        node3.next = node4;
        this.head = node1;
    }

    public void show() {
        Node cur = this.head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void show2(Node newHead) {
        Node cur = newHead;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    public int getSize() {
        int count = 0;
        Node cur = this.head;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        Node cur=this.head;
        while (cur!=null){
            if (cur.val==key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //头插法
    public void addFirst(int data) {
        Node cur = new Node(data);
        cur.next=this.head;
         this.head=cur;
    }
    //尾插法
    public void addLast(int data) {
        Node node = new Node(data);
        Node cur = this.head;
        if (this.head==null){
            this.head=node;
            return;
        }
        while (cur.next!=null){
            cur=cur.next;
        }
        cur.next=node;
    }
    //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index,int data) {
        Node node = new Node(data);
        Node cur=this.head;
        if (index<0 || index>getSize()){
            System.out.println("index输入不合法");
            return false;
        }
        if (index==0){
            addFirst(data);
            return true;
        }
        if (index==getSize()){
            addLast(data);
            return true;
        }
        for (int i = 0; i <index-1; i++) {
             cur=cur.next;
        }
        node.next=cur.next;
        cur.next=node;
        return true;
    }


    //删除第一次出现关键字为key的节点
    public void remove(int key) {
         if (head.val==key){
             this.head=this.head.next;
             return;
        }
        Node prev=searchPrev(key);
        if (prev==null){
            System.out.println("没有你要删除的结点");
            return;
        }else{
            prev.next=prev.next.next;
        }
    }
    //寻找要删除的元素key
    private Node searchPrev(int key){
        Node cur=this.head;
        while (cur.next!=null){
            if (cur.next.val==key) {
                return cur;
            }
            cur=cur.next;
        }
        return null;
    }

    //删除所有值为key的节点
    public Node removeAllKey(int key) {
        judge();
        Node cur=this.head.next;
        Node prev=this.head;
        while (cur!=null){
           if (cur.val==key){
              prev.next=cur.next;
           }else {
               prev=cur;
           }
            cur=cur.next;
        }
        if (this.head.val==key){
            this.head=this.head.next;
        }
        return head;
    }
    public void clear() {
        this.head=null;
    }
    //反转单链表
    public Node reverseList(){
        judge();
        Node prev=null;
        Node curNext=null;
        Node cur=this.head;
        while (cur!=null){
            curNext=cur.next;
            cur.next=prev;
            prev=cur;
            cur=curNext;
        }
        return prev;
    }
    //判断单链表是否为空
    private Node judge() {
        if (this.head == null) {
            return null;
        }
        return head;
    }
        //寻找该单链表中间vel值（有两个取第二个）
        public Node middle () {
            judge();
            Node fast = this.head;
            Node slow = this.head;
            while (fast != null && fast.next != null) {
                fast = fast.next.next;
                slow = slow.next;
            }
            return slow;
        }

        //寻找该单链表的倒数第N个元素
        public Node rec (int n) {
            judge();
            Node fast = this.head;
            Node slow = this.head;
            if (n<=0 ){
                System.out.println("没有您要找的元素！！");
                return null;
            }
            while ( n-1!=0){
                if (fast==null){
                    System.out.println("没有您要找的元素！！");
                    return null;
                }
               fast=fast.next;
               n--;
            }
            while (fast.next != null) {
                fast = fast.next;
                slow = slow.next;
            }
            return slow;
        }
    //将两个（有序）单链表，和并成一个有序单链表
    public Node merge (Node headA,Node headB) {
        Node newHead=new Node(-1);
        Node tmp=newHead;
        while (headA!=null && headB!=null){
            if (headA.val<headB.val){
                tmp.next=headA;
                headA=headA.next;
            }else{
                tmp.next=headB;
                headB=headB.next;
            }
            tmp=tmp.next;
        }
        if (headA==null){
            tmp.next=headB;
        }else {
            tmp.next=headA;
        }
         return newHead.next;
    }

    //输入一个n，将链表中val值 小于n的放在前边，大于的放在后边。（并且不打乱原来顺序）
    public  Node partition(int n){
        Node cur=this.head;
        Node as=null;
        Node ae=null;

        Node bs=null;
        Node be=null;

        while (cur!=null){
            if (cur.val<n){
                if (as==null){
                    as=cur;
                    ae=cur;
                }else {
                    as.next=cur;
                    ae=ae.next;
                }
            }else {
                if (cur.val<n){
                    bs=cur;
                    be=cur;
                }else {
                    bs.next=cur;
                    be=be.next;
                }
            }
            cur=cur.next;
        }
        if (as==null){
            return bs;
        }
        ae.next=bs;
        if (bs!=null){
            be.next=null;
        }
        return as;
    }

        public static void main (String[]args){
            MyLinkedList myLinkedList = new MyLinkedList();
            myLinkedList.addLast(5);
            myLinkedList.addLast(8);
            myLinkedList.addLast(9);
            myLinkedList.addLast(10);
            myLinkedList.show();
            MyLinkedList myLinkedList1 = new MyLinkedList();
            myLinkedList1.addLast(2);
            myLinkedList1.addLast(3);
            myLinkedList1.addLast(11);
            myLinkedList1.addLast(12);
            myLinkedList1.show();
            Node ret = myLinkedList.partition(5);
            myLinkedList1.show2(ret);
        }
    }