Implementation and test code of headless doubly linked list
1. Head insertion method
2. Tail insertion method
3. Insert at any position, the first data node is subscript 0
4. Find whether the keyword key is included in the singly linked list
5. Delete the first occurrence of the keyword as key node
6. remove all the key value of the node
7. the resulting single chain length
8. Print list
9. empty list
Implementation code
class ListNode{
private int val;
private ListNode prev;
private ListNode next;
public ListNode(int val) {
this.val = val;
}
public int getVal() {
return val;
}
public ListNode getNext() {
return next;
}
public ListNode getPrev() {
return prev;
}
public void setVal(int val) {
this.val = val;
}
public void setPrev(ListNode prev) {
this.prev = prev;
}
public void setNext(ListNode next) {
this.next = next;
}
}
public class DoubleLinkedList {
private ListNode head;
private ListNode last;
//头插法
public void addFirst(int data){
ListNode node = new ListNode(data);
if(this.head == null){
this.head = node;
this.last = node;
}else {
//node.next = this.head;
node.setNext(this.head);
head.setPrev(node);
head = node;
}
}
public void display(){
ListNode cur =this.head;
while (cur != null){
System.out.print(cur.getVal() + " ");
cur = cur.getNext();
}
System.out.println();
}
// 尾插法
public void addLast(int data){
ListNode node = new ListNode(data);
if(this.head == null){
this.head = node;
this.last = node;
}else{
last.setNext(node);
node.setPrev(last);
this.last = node;
}
}
//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){
if (index < 0 || index > size()){
return;
}
if(index == 0){
addFirst(data);
return;
}
if(index == size()){
addLast(data);
return;
}
ListNode cur = this.head;
while (index != 0){
cur = cur.getNext();
index--;
}
ListNode node =new ListNode(data);
node.setNext(cur);
node.setPrev(cur.getPrev());
node.getPrev().setNext(node);
cur.setPrev(node);
}
//查找是否包含关键字key是否在单链表当中
public boolean contains(int key){
ListNode cur = this.head;
while (cur != null){
if (cur.getVal() == key){
return true;
}
cur= cur.getNext();
}
return false;
}
public ListNode findNode(int key) {
ListNode cur = this.head;
while (cur != null) {
if(cur.getVal() == key) {
return cur;
}
cur = cur.getNext();
}
return null;
}
//删除第一次出现关键字为key的节点
public void remove(int key){
ListNode cur = this.findNode(key);
if(cur == null) {
return;
}
//
if(cur == this.head) {
this.head = this.head.getNext();
//this.head.prev = null;
this.head.setPrev(null);
return;
}
if(cur == this.last) {
cur.getPrev().setNext(null);
this.last = this.last.getPrev();
return;
}
cur.getPrev().setNext(cur.getNext());
cur.getNext().setPrev(cur.getPrev());
}
// 删除所有值为key的节点
public void removeAllKey(int key){
ListNode cur = this.head;
while (cur != null) {
if(cur.getVal() == key) {
if(cur == this.head) {
//头结点
this.head = this.head.getNext();
this.head.setPrev(null);
}else {
cur.getPrev().setNext(cur.getNext());
if(cur.getNext() != null) {
cur.getNext().setPrev(cur.getPrev());
}else {
//cur.next == null
this.last = this.last.getPrev();
}
}
}
cur = cur.getNext();
}
}
// 得到单链表的长度
public int size(){
ListNode cur = this.head;
int count = 0;
while (cur != null){
count++;
cur = cur.getNext();
}
return count;
}
public void clear(){
ListNode cur = this.head;
while (cur != null) {
ListNode curNext = cur.getNext();
cur.setNext(null);
cur.setPrev(null);
cur = curNext;
}
this.last = null;
this.head = null;
}
}
Test code:
import com.sun.org.apache.xerces.internal.dom.PSVIAttrNSImpl;
import java.util.Arrays;
import java.util.LinkedList;
public class TestDemo {
public static void main(String[] args) {
DoubleLinkedList doubleLinkedList = new DoubleLinkedList();
doubleLinkedList.addLast(12);
doubleLinkedList.addLast(32);
doubleLinkedList.addLast(12);
doubleLinkedList.addLast(52);
doubleLinkedList.addLast(12);
doubleLinkedList.display();
System.out.println("===============");
doubleLinkedList.clear();
doubleLinkedList.display();
//doubleLinkedList.removeAllKey(12);
//doubleLinkedList.display();
//doubleLinkedList.remove(32);
//doubleLinkedList.display();
// doubleLinkedList.remove(12);
//doubleLinkedList.display();
//doubleLinkedList.addIndex(3,45);
//System.out.println(doubleLinkedList.contains(12));
}
}
Screenshot of the empty method:
