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 *h = head;
        while(h){
            RandomListNode *node = new RandomListNode(h->label);
            node->next = h->next;
            h->next = node;
            h = h->next->next;
        }
        h = head;
        while(h){
            if(h->random)
                h->next->random = h->random->next;
            h = h->next->next;
        }
        RandomListNode *ans, *tmp;
        h = head;
        tmp = h->next;
        ans = tmp;
        h->next = h->next->next;
        h = h->next;
        while(h){
            tmp->next = h->next;
            h->next = h->next->next;
            tmp = tmp->next;
            h = h->next;
        }
        return ans;
    }
};