leetcode--011 copy list with random pointer

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 package leetcode;

 class RandomListNode {
     int label;
     RandomListNode next, random;

     public RandomListNode(int x) {
         this.label = x;
     }
 }

 public class CopyListRandom {
     public RandomListNode copyRandomList(RandomListNode head) {
         if(head==null)return head;
         RandomListNode po= head.next;
         RandomListNode p=head;
         while(p!=null){
             RandomListNode newnode=new RandomListNode(p.label);
             po=p.next;
             newnode.next=p.next;
             p.next=newnode;

             p=po;
         }
         p=head;
         while(p!=null){
             if(p.random!=null){
             p.next.random=p.random.next;
         }
             p=p.next.next;
         }
         p=head;
         RandomListNode h=head.next;
         RandomListNode q=h;
         while(q!=null){
             p.next=q.next;
             p=q;
             q=q.next;
         }
         return h;
     }
 }