Copy List with Random Pointer

/**
 * Definition for singly-linked list with a random pointer.
 * struct RandomListNode {
 *     int label;
 *     RandomListNode *next, *random;
 *     RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
 * };
 */
class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {
        if(head == NULL) return NULL;
        RandomListNode *head2, *p, *p2;
        p = head2 = head;
        while(p) {
            RandomListNode *s = new RandomListNode(p->label);
            s->next = p->next;
            p->next = s;
            p = s->next;
        }
        p = head;
        while(p) {
            if(p->random) p->next->random = p->random->next;
            p = p->next->next;
        }
        head2 = p2 = head->next; p = head;
        while(p) {
            p->next = p->next->next;
            p = p->next;
            if(p2->next) {
                p2->next = p2->next->next;
                p2 = p2->next;
            }
        }
        return head2;
    }
};