【面试准备】letcode-Copy List with Random Pointer

参照http://www.cnblogs.com/easonliu/p/3647160.html

/**
 * 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* p1 = head;
        RandomListNode* p2 = head->next;
        
        while(p1 != NULL){
            p1->next = new RandomListNode(p1->label);
            p1->next->next = p2;
            p1 = p2;
            if(p1 != NULL){
                p2 = p1->next;
            }
        }
        p1 = head;
        p2 = head->next;
        while(p1 != NULL){
            if(p1->random == NULL){
                p2->random = NULL;
            }else{
                p2->random = p1->random->next;
            }
            p1 = p2->next;
            if(p1 != NULL){
                p2 = p1->next;
            }
        }
        RandomListNode* ans = head->next;
        p1 = head;
        p2 = head->next;
        while(p2 != NULL){
            p1->next = p2->next;
            p1 = p2;
            if(p2 != NULL){
                p2 = p2->next;
            }
        }
        p1->next = NULL;
        return ans;
    }
};