Leetcode Copy list with random pointer

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

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[code]

/**
 * Definition for singly-linked list with a random pointer.
 * class RandomListNode {
 *     int label;
 *     RandomListNode next, random;
 *     RandomListNode(int x) { this.label = x; }
 * };
 */
public class Solution {
    public RandomListNode copyRandomList(RandomListNode head) {
        if(head==null)return null;
        RandomListNode p=head;
        while(p!=null)
        {
            RandomListNode next=p.next;
            p.next=new RandomListNode(p.label);
            p.next.next=next;
            p=next;
        }
        p=head;
        RandomListNode newHead=p.next, q=newHead;
        while(true)
        {
            q.random= p.random==null ? null : p.random.next;
            p=q.next;
            if(p==null)break;
            q=p.next;
        }
        p=head;
        q=newHead;
        while(true)
        {
            RandomListNode next=q.next;
            q.next=next==null ? null :next.next;
            p.next=next;
            p=next;
            if(p==null)break;
            q=p.next;
        }

        return newHead;
    }
}

[Thoughts]
copy random 和 复原 原list不能同时进行， 因为p.random是前面的node, p.random.next 就错了