/**
* Created with IntelliJ IDEA.
* User: guohairui
* Date: 17-2-26
* Time: 下午3:21
* To change this template use File | Settings | File Templates.
*/
public class MyLinkedList {
private Node head=new Node(null,null,null);
public int size = 0;
public MyLinkedList(){
head.next=head.previous=head;
}
public void add(Object o){
if(null==head){
head = new Node(null,null,null);
}
Node newNode = new Node(o,head,head.previous); //放在最后
newNode.previous.next=newNode;
newNode.next.previous=newNode;
size++;
}
public void add(int index,Object o ) {
Node newNode = new Node(o,getNode(index),getNode(index).previous); //放在最后
newNode.previous.next=newNode;
newNode.next.previous=newNode;
size++;
}
public Object get(int index){
return getNode(index).data;
}
public Object remove(int index){
remove(getNode(index));
return null;
}
public void addFirst(Object o){
}
public void removeFirst(){
remove(head.next);
}
public void removeLast(){
remove(head.previous);
}
public void remove(Node node){
node.previous.next=node.next;
node.next.previous=node.previous;
size--;
}
public int size(){
return size();
}
public Object[] toArray(){
return null;
}
public Node getNode(int index){
if(index<0||index>=size)
throw new RuntimeException("超出范围了");
Node node = head;
if(index<(size>>1)){//当偏向于前一半时从头找，否则从尾找
for ( int i=0;i<=index;i++) {
node = node.next;
}
}else {
for (int i=size;i>index;i--){
node=node.previous;
}
}
return node;
}
private static class Node{
Object data;//当前Entry
Node next;//下一个
Node previous;//前一个
public Node(Object data,Node next,Node previous){
this.data=data;
this.next=next;
this.previous=previous;
}
}
public String toString(){
StringBuilder sb = new StringBuilder();
sb.append('[');
Node n =getNode(0) ;
for (int i=0;i<size;i++) {
sb.append(n.data);
if(i<size-1)
sb.append(",");
n=n.next;
}
return sb.append(']').toString();
}
}