一 LinkedList
LinkedList的方法的实现
1.头插法
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
@Override
public void addFirst(int data) {
ListNode node=new ListNode(data);
ListNode cur=head;
if (head==null) {
head = last = cur;
} else{
node.next=head;
head.prev=node;
head=node;
}
}
}2.尾插法
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public void addLast(int data) {
ListNode node=new ListNode(data);
ListNode cur=head;
if (head==null) {
head = last = cur;
} else{
node.prev=last;
last.next=node;
last=node;
}
}
}3.任意位置插入,第一个数据节点为0号下标
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public void addIndex(int index, int data) {
ListNode node=new ListNode(data);
int len=size();
if(index<0 || index>len){
return;
}
if(index==0){
addFirst(data);
}
if(index==len){
addLast(data);
}
ListNode cur=head;
node.next=cur;
node.prev=cur.prev;
cur.prev.next=node;
cur.prev=node;
}4.查找是否包含关键字key是否在链表当中
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public boolean contains(int key) {
ListNode cur=head;
while (head!=null){
if(head.val==key){
return true;
}
head=head.next;
}
return false;
}5.得到链表的长度
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public int size() {
ListNode cur=head;
int count=0;
while (head!=null){
count++;
head=head.next;
}
return count;
}6.打印链表
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public void display() {
ListNode cur=head;
while (head!=null){
System.out.println(head.val+" ");
head=head.next;
}
}7.删除第一次出现关键字为key的节点
删除中间部分
删除头
并且考虑只有一项的情况下
删除尾
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public void remove(int key) {
ListNode cur=head;
while (cur!=null){
if(cur.val==key){
if(cur==head){
head=head.next;
if(head!=null) {
head.prev=null;
}
}else {
if(cur.next==null){
cur.prev.next=null;
last=last.prev;
}else {
cur.prev.next=cur.next;
cur.next.prev=cur.prev;
}
}
return;
}
cur=cur.next;
}
}
}8.删除所有值为key的节点
跟remove基本一样，删去return就行了，将整个链表检查一遍，删去全部的key
public void removeAllKey(int key) {
ListNode cur=head;
while (cur!=null){
if(cur.val==key){
if(cur==head){
if(head!=null) {
cur.next.prev = null;
}
}else {
if(cur.next==null){
cur.prev.next=null;
last=last.prev;
}else {
cur.prev.next=cur.next;
cur.next.prev=cur.prev;
}
}
}
cur=cur.next;
}
}9.清空链表
public class MyLinkedList implements IList{
static class ListNode{
public int val;
public ListNode next;
public ListNode prev;
public ListNode(int val){
this.val=val;
}
}
public ListNode head;
public ListNode last;
public void clear() {
ListNode cur=head;
while (cur!=null){
ListNode curN=cur.next;
cur.prev=null;
cur.next=null;
cur=curN;
}
}
}
LinkedList方法的使用
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
List<Integer> list=new LinkedList();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
ArrayList<Integer> list1=new ArrayList<>();
list1.add(1);
list1.add(2);
list1.add(3);
list1.add(4);
linkedList.addAll(list1);
System.out.println(linkedList);
linkedList.remove(2);
linkedList.get(3);
linkedList.set(2,6);
linkedList.contains(5);
linkedList.size();
linkedList.clear();
}LinkedList的遍历
1.for循环遍历
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
for (int i = 0; i < linkedList.size(); i++) {
System.out.println(linkedList.get(i)+" ");
}
}2.foreach遍历
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
for (Integer x:linkedList) {
System.out.print(x+" ");
}
}
}3.迭代器
Iterator
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
Iterator<Integer> iterator=linkedList.iterator();
while (iterator.hasNext()){
System.out.print(iterator.next());
}ListIterator
1.按顺序打印
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
ListIterator<Integer> it=linkedList.listIterator();
while (it.hasNext()){
System.out.println(it.next()+" ");
}2.逆序打印
public class Test {
public static void main(String[] args) {
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.add(1);
linkedList.addFirst(3);
linkedList.addLast(6);
ListIterator<Integer> it1=linkedList.listIterator();
while (it1.hasPrevious()){
System.out.println(it1.previous()+" ");
}
}注: ListIterator可以当作迭代器的原因是，它是Iterator的子类，专门用来打印List类的。
ArrayList和LinkedList的区别
当你进行查找时，我建议你选择ArrayList，因为LinkedList访问任意元素需要从头或尾遍历链表，时间复杂度为 O(n)，ArrayList可以通过索引直接访问任意元素，时间复杂度是 O(1)。
当我们经常使用插入等功能，可以使用LinkedList，如果在末尾插入或删除元素，效率较高（时间复杂度 O(1)），ArrayList需要移动大量元素，因此效率较低（时间复杂度 O(n)）。
希望能对大家有所帮助！！！！
