链表的底层实现
此程序是头插法实现的链表且含有虚拟头节点
public class LinkedList<E> {
private class Node<E>{
E e;
Node next;
public Node (E e,Node next){
this.e=e;
this.next=next;
}
public Node(E e){
this(e,null);
}
public Node(){
this(null,null);
}
@Override
public String toString() {
return e.toString();
}
}
private Node dummyHead;
private int size;
public LinkedList(){
dummyHead=new Node(null,null);
size=0;
}
public int getSize(){
return size;
}
public boolean isEmpty(){
return size==0;
}
public void add(int index,E e){
if(index<0 ||index>size)
throw new IllegalArgumentException("Add Fail,Index error!");
Node prev=dummyHead;
for(int i=0; i<index; i++) {
prev=prev.next;
}
// Node node =new Node(e);
// node.next=prev.next;
// prev.next=node;
prev.next=new Node(e,prev.next);
size++;
}
public void addLast(E e){
add(size,e);
size++;
}
public void addFirst(E e){
add(0,e);
size++;
}
public Node get(int index) {
if(index<0 ||index>size)
throw new IllegalArgumentException("Get Fail,Index error!");
Node cur=dummyHead.next;
for (int i=0; i<index;i++){
cur=cur.next;
}
return cur;
}
public Node getFirst(){
return get(0);
}
public Node getLast(){
return get(size-1);
}
public void set(int index,E e){
if(index<0 ||index>size)
throw new IllegalArgumentException("Set Fail,Index error!");
Node cur=dummyHead.next;
for (int i=0; i<index;i++){
cur.e=e;
}
}
public boolean contains(E e) {
Node cur=dummyHead.next;
while(cur!=null) {
if(cur.e.equals(e)){
return true;
}
cur=cur.next;
}
return false;
}
public E remove(int index){
if(index<0 ||index>size)
throw new IllegalArgumentException("Get Fail,Index error!");
Node prev=dummyHead;
for(int i=0;i<index; i++){
prev=prev.next;
}
Node retNode=prev.next;
prev.next=retNode.next;
retNode.next=null;
size--;
return (E) retNode.e;
}
@Override
public String toString(){
StringBuilder res = new StringBuilder();
Node cur =dummyHead.next;
while(cur != null){
res.append(cur +"->");
cur = cur. next ;
}
res.append( "NULL");
return res.toString();
}
public static void main(String[] args){
LinkedList<Integer> linkedList=new LinkedList<>();
linkedList.addFirst(1);
linkedList.addFirst(2);
linkedList.addFirst(3);
linkedList.addFirst(4);
linkedList.addFirst(5);
System.out.println(linkedList);
linkedList.remove(2);
System.out.println(linkedList);
}
}
输出结果