一 链表
1.. ArrayList的缺陷（LinkedList的优点）
在ArrayList任意位置插入或者删除元素时，就需要将后序元素整体往前或者往后 搬移，时间复杂度为O(n)，效率比较低，因此ArrayList不适合做任意位置插入和删除比较多的场景。
2.什么是链表
链表是一种物理存储结构上非连续存储结构，数据元素的逻辑顺序是通过链表中的引用链接次序实现的 。我们可以把链表想象成火车的车厢连接在一起。
3.链表的八种形式
最常用的为单向链表
还有双向链表，带头或者不带头链表，循环或者非循环链表
4.链表的实现
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);
//得到单链表的长度
public int size();
public void clear();
public void display();
}1.头插法
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void addFirst(int data) {
ListCode node=new ListCode(data);
node.next=head;
head=node;
}
}2.尾插法
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void addLast(int data) {
ListCode cur=head;
ListCode node=new ListCode(data);
if(cur==null){
head=node;
return;
}
while (cur!=null){
cur=cur.next;
}
cur.next=node;
}
}3.得到单链表的长度
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public int size() {
int len=0;
ListCode cur=head;
while (cur!=null){
len++;
cur=cur.next;
}
return len;
}
}4.任意位置插入,第一个数据节点为0号下标
public class IllegalException extends RuntimeException{
public IllegalException(){
}
public IllegalException(String mas){
super(mas);
}
}
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void addIndex(int index, int data) throws IllegalException{
try {
int len=size();
if(index<0 || index>len){
throw new IllegalException("pos位置不合法");
}
if(len==0){
addFirst(data);
}
if (index==len-1){
addLast(data);
}
ListCode node=new ListCode(data);
ListCode cur=head;
while (index!=0){
cur=cur.next;
index--;
}
node.next=cur.next;
cur.next=node;
}catch (IllegalException e){
e.printStackTrace();
System.out.println("pos位置不合法");
}
}
}5.查找是否包含关键字key是否在单链表当中
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public boolean contains(int key) {
ListCode cur=head;
while (cur!=null){
if (cur.val==key){
return true;
}
}
return false;
}
}6.删除第一次出现关键字为key的节点
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void remove(int key) {
if (head==null){
return;
}
if(head.val==key){
return;
}
ListCode cur=findNodeOfKey(key);
if(cur==null){
return;
}
ListCode del=cur.next;
cur.next=del.next;
}
public ListCode findNodeOfKey(int key){
ListCode cur=head;
while (cur.next!=null){
if(cur.next.val==key){
return cur;
}
cur=cur.next;
}
return null;
}
}7. 删除所有值为key的节点
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void removeAllKey(int key) {
if(head==null){
return;
}
ListCode cur=head.next;
ListCode pre=head;
while (cur!=null){
if(cur.val==key){
pre.next=cur.next;
cur=cur.next;
}else {
pre=cur;
cur=cur.next;
}
}
if(head.val==key){
head=head.next;
}
}
}8.清空单链表
public class MyArrayList implements IList {
static class ListCode {
public int val;
public ListCode next;
public ListCode(int val) {
this.val = val;
}
}
public ListCode head;
public void clear() {
ListCode cur=head;
while (cur.next!=null){
ListCode cun1=cur;
cur.next=null;
cur=cun1.next;
}
head=null;
}
}希望能对大家有所帮助！！！！
