copy a random link

题目：

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) {
        if(head == NULL) return NULL;
        //将新节点复制到原来节点后面
        RandomListNode *copy;
        RandomListNode *p = head;
        RandomListNode *tmp;
        while(p!=NULL)
        {
            copy = new RandomListNode(p->label);
            tmp = p->next;
            p->next = copy;
            copy->next = tmp;
            p = tmp;
        }
        //将新结点与随机结点相连接     
        p = head;
        copy = head->next;
        while(p!=NULL && copy!=NULL)
        {
            copy->random = ((p->random)?p->random->next:NULL);
            p = ((copy->next)?copy->next:NULL);
            copy = ((p->next)?p->next:NULL);
        }
        //将新节点与原结点拆开
        p = head;
        head = copy = head->next;
        while(p!=NULL && copy!=NULL)
        {
            p->next = ((copy->next)?copy->next:NULL);
            p = ((p->next)?p->next:NULL);
            copy->next = ((p)?p->next:NULL);
            copy = ((copy->next)?copy->next:NULL);
        }
        return head;
    }
};