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.

剑指offer里面的一道题，具体思路看不懂请查阅剑指offer

/**
 * 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:
    void copyFirst(RandomListNode *head){
        
        RandomListNode *pcur, *pnext, *q;
        pcur = head;
        while(pcur != NULL){
            pnext = pcur->next;
            q = new  RandomListNode(pcur->label);
            q->next = pnext;
            pcur->next = q;
            pcur = pnext;
        }
    }
    void fixRandom(RandomListNode * head){
        
        RandomListNode *ph = head;
        while(ph!=NULL){
            if(ph->random != NULL)
                ph->next->random = ph->random->next;
            ph = ph->next->next;    
        }
    }
    RandomListNode * getCopy(RandomListNode *head){
            
        RandomListNode *p,*rcur,*q, *res;
        res = NULL; p = head;rcur = NULL;
        while(p != NULL){
            q  = p->next;
            p->next = q->next;
            p = p->next;
            if(res == NULL){
                res = q;
                rcur = q;
            }else{
                rcur->next = q;
                rcur = q;
            }
        }
       // rcur->next = NULL;
        return res;
        
    }
    RandomListNode *copyRandomList(RandomListNode *head) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if(head == NULL) return NULL;
        copyFirst(head);
        fixRandom(head);
        return getCopy(head);
        
    }
};