leetcode[138]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.

/**
 * 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) {
        RandomListNode *p=head;
        RandomListNode *pnext=NULL;
        RandomListNode *tmp=NULL;
        while(p)
        {
            pnext=p->next;
            tmp=new RandomListNode(p->label);
            p->next=tmp;
            tmp->next=pnext;
            p=pnext;
        }
        p=head;
        while(p)
        {
            if(p->random)p->next->random=p->random->next;
            p=p->next->next;
        }
        RandomListNode *newhead=new RandomListNode(0);
        pnext=newhead;
        p=head;
        while(p)
        {
            pnext->next=p->next;
            pnext=pnext->next;
//            if(pnext->next)p->next=pnext->next;
//            else p->next=NULL;
            p->next=pnext->next;//
            p=p->next;
        }
        return newhead->next;
    }
};