MyLinkedList.java文件
class ListNode {
public int val;
public ListNode prev;
public ListNode next;
public ListNode(int val) {
this.val = val;
}
}
public class MyLinkedList {
public ListNode head;//指向双向链表的头节点
public ListNode last;//指向的是尾巴节点
public void display() {
ListNode cur = this.head;
while (cur != null) {
System.out.print(cur.val+ " ");
cur = cur.next;
}
System.out.println();
}
//得到单链表的长度
public int size() {
int count = 0;
ListNode 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){
ListNode 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) {
//分为两种情况
ListNode node = new ListNode(data);
if (head == null) {
this.head = node;
this.last = node;
}else {
node.next = head;
head.prev = node;
head = node;
}
}
//尾插法
public void addLast(int data){
ListNode node = new ListNode(data);
if (head == null) {
this.head = node;
this.last = node;
}else {
this.last.next = node;
node.prev = this.last;
this.last = node;
}
}
//删除第一次出现关键字为key的节点
public void remove(int key){
if (head == null) {
return;
}
ListNode cur = this.head;
while (cur != null) {
if (cur.val == key) {
if (cur == head) {
head = head.next;
if (head != null) {
//如果只有一个node，被删掉了，可能会被空指针异常
head.prev = null;
}else {
last = null;
}
}else if (cur == last){
cur.prev.next = cur.next;
last = last.prev;
}else {
cur.prev.next = cur.next;
cur.next.prev = cur.prev;
}
return;
}else {
cur = cur.next;
}
}
}
//删除所有值为key的节点
public void removeAllKey(int key){
if (head == null) {
return;
}
ListNode cur = this.head;
while (cur != null) {
if (cur.val == key) {
if (cur == head) {
head = head.next;
if (head != null) {
//如果只有一个node，被删掉了，可能会被空指针异常
head.prev = null;
}else {
last = null;
}
}else if (cur == last){
cur.prev.next = cur.next;
last = last.prev;
}else {
cur.prev.next = cur.next;
cur.next.prev = cur.prev;
}
}else {
cur = cur.next;
}
}
}
public ListNode searchIndex (int index) {
if (index < 0 || index > size()) {
System.out.println("index位置不合法！");
return null;
}
ListNode cur = this.head;
while (index != 0) {
index--;
cur = cur.next;
}
return cur;
}
//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){
ListNode node = new ListNode(data);
ListNode cur;
cur = searchIndex(index);
if (index == 0) {
addFirst(data);
}else if (index == size()) {
addLast(data);
}else {
node.next = cur;
node.prev = cur.prev;
cur.prev.next = node;
cur.prev = node;
// node.next = cur.prev.next;
// cur.prev.next = node; //两种都行
// node.prev = cur.prev;
// cur.prev = node;
}
}
//暴力的做法是直接将head和last直接置为null
//温柔的做法将所有节点置为null
public void clear() {
ListNode cur = this.head;
while (cur != null) {
ListNode curNext = head.next;
cur.next = null;
cur.prev = null;
cur = curNext;
}
head = null;
last = null;
}
//clear的第二种写法
public void clear2() {
while (head != null) {
ListNode curNext = head.next;
head.next = null;
head.prev = null;
head = curNext;
}
last = null;
}
}
TestDemo.java文件
public class TestDemo {
public static void main(String[] args) {
MyLinkedList myLinkedList = new MyLinkedList();
myLinkedList.addLast(1);
myLinkedList.addLast(2);
myLinkedList.addLast(3);
myLinkedList.addLast(4);
myLinkedList.display();
myLinkedList.remove(2);
myLinkedList.display();
// myLinkedList.addIndex(7,77);
// myLinkedList.display();
}
}
//class Test1 {
// public static int aaa;
// public static void bbb() {
// System.out.println("111");
// }
//}
//public class TestDemo{
// static boolean Paddy;
// public static void ccc() {
// System.out.println("111");
// }
// public static void main(String args[]){ //内部类的静态方法可以直接通过方法名进行访问吗？ 可以
System.out.println(test.aaa);
// ccc();
System.out.println(ccc());
// }
//public class TestDemo{
//
// private static int count;
// private static void as() {
// System.out.println("666");
// }
//
// public static void main(String[] args) {
//
// TestDemo test=new TestDemo(88);
// System.out.println(count);
// test.as();
// Test1 ass = new Test1();
// ass.bbb();
//
System.out.println(test.count);
//
// }
//
// TestDemo(int a) {
//
// count=a;
//
// }
//}