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手动实现LinkedList

web 2025/7/18 6:21:58

前言

大家好，我是Maybe。最近在学习数据结构中的链表，自己手动实现了一个LinkedList。我想与大家分享一下。

思维导图

代码部分

package Constant;public class constant {public static final String INDEX_IS_WRONG="输入的下标不合法";
}

package utils;public class IndexException extends RuntimeException{public IndexException() {super();}public IndexException(String message) {super(message);}
}

public interface IList {// 头插法public void addFirst(int data);// 尾插法public void addLast(int data);// 任意位置插入，第一个数据节点为0号下标public void addIndex(int index,int data);// 查找是否包含关键字key是否在单链表当中public boolean contains(int key);// 删除第一次出现关键字为key的节点public void remove(int key);// 删除所有值为key的节点public void removeAllKey(int key);// 得到链表的长度public int size();public void display();public void clear();
}

import Constant.constant;
import utils.IndexException;public class LinkedList implements IList {//1.定义一个内部类static class ListNode{public int val;//类型写成了String,应该是ListNode的public ListNode prev;public ListNode next;public ListNode(int val) {this.val = val;}}public ListNode head;//这个就要给个尾了public ListNode last;@Overridepublic void addFirst(int data) {if(head==null){ListNode node=new ListNode(data);head=last=node;}else{ListNode node=new ListNode(data);node.next=head;head.prev=node;head=node;}}@Overridepublic void addLast(int data) {if(head==null){ListNode node=new ListNode(data);//写成了node=last=null了head=last=node;}else{ListNode node=new ListNode(data);last.next=node;node.prev=last;//这里要注意last=last.next;}}@Override//在LinkedList中找到对应的cur，然后再cur之前插入public void addIndex(int index, int data) {int len=size();if(index<0||index>len){String msg= constant.INDEX_IS_WRONG+index;throw new IndexException(msg);}if(index==0){addFirst(data);}else if(index==len){addLast(data);}else{ListNode node=new ListNode(data);ListNode cur=findIndex(index);node.next=cur;cur.prev.next=node;node.prev=cur.prev;cur.prev=node;}}//在LinkedList中找到对应的curprivate ListNode findIndex(int index){if(head==null){return null;}else{ListNode cur=head;while(index!=0){cur=cur.next;index--;}return cur;}}@Overridepublic boolean contains(int key) {if(head==null){return false;}else{ListNode cur=head;while(cur!=null){if(cur.val==key){return true;}else{cur=cur.next;}}return false;}}@Overridepublic void remove(int key) {//1.先判断链表是否为空if(head==null){return;}else{ListNode cur=head;while(cur!=null){if(cur.val==key){//1.考虑头删的情况if(cur==head){head=head.next;//考虑如果链表中只有一个节点的情况if(head!=null){head.prev=null;}}else{cur.prev.next=cur.next;//尾巴节点和中间节点共用if(cur.next==null){//尾节点last=last.prev;}else{//中间节点cur.next.prev=cur.prev;}}return;}cur=cur.next;}}}@Overridepublic void removeAllKey(int key) {if(head==null){return;}else{ListNode cur=head;while(cur!=null){if(cur.val==key){if(cur==head){head=head.next;//只有一个节点的情况要考虑if(head!=null){head.prev=null;}}else{cur.prev.next=cur.next;if(cur.next==null){last=last.next;}else{cur.next.prev=cur.prev;}}}cur=cur.next;}}}@Overridepublic int size() {if(head==null){return 0;}else{ListNode cur=head;int count=0;while(cur!=null){cur=cur.next;count++;}return count;}}@Overridepublic void display() {if(head==null){return;}else{ListNode cur=head;while(cur!=null){System.out.print(cur.val+" ");cur=cur.next;}System.out.println();}}@Overridepublic void clear() {if(head==null){return;}else{ListNode cur=head;while(cur!=null){ListNode curN=cur.next;cur.prev=null;cur.next=null;cur=curN;}head=last=null;//最后要把head和last置为null}}
}

import utils.IndexException;public class Test {public static void main(String[] args) {LinkedList linkedList=new LinkedList();linkedList.addLast(1);linkedList.addLast(1);linkedList.addLast(1);linkedList.addLast(2);linkedList.display();
//        linkedList.addFirst(1);
//        linkedList.addFirst(2);
//        linkedList.addFirst(3);
//        linkedList.addFirst(4);
//        linkedList.display();
//        int ret=linkedList.size();
//        System.out.println(ret);
//        try{
//            linkedList.addIndex(2,100);
//
//        }catch (IndexException e){
//            e.printStackTrace();
//        }
//        linkedList.display();
//        linkedList.remove(1);
//        linkedList.display();
//        linkedList.removeAllKey(1);linkedList.clear();linkedList.display();}
}