leetcode--011 copy list with random pointer

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;
    }
}