双向链表

class NodeList{

int val;

NodeList next ,prev

NodeList（int val ）{

this.val=val;

next=prev=null;

}

public NodeList inverse(NodeList head){

ListNode temp = new NodeList();

while(head.next!=null){

temp = head;

head=head.next;

temp.prev=temp.next;

prev=head;

}

}

}