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.

主要是深层复制的问题：

本题比较简单，具体实现见代码：

/**
 * 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* pNode = head;
		map<RandomListNode*,RandomListNode*>node_map;
		if (pNode)
		{
			RandomListNode* NewHead = NULL;
			NewHead = new RandomListNode(pNode->label);
			node_map.insert(make_pair(pNode,NewHead));

			RandomListNode* pNewNode = NewHead;
			while (pNode->next)
			{
				pNode = pNode->next;
				RandomListNode* new_node = new RandomListNode(pNode->label);
				pNewNode->next = new_node;
				pNewNode = pNewNode->next;
				node_map.insert(make_pair(pNode,pNewNode));
			}
			pNode = head;
			pNewNode = NewHead;
			while (pNode)
			{
				if (pNode->random != NULL)
				{
					pNewNode->random = node_map.find(pNode->random)->second;
				}
				pNode = pNode->next;
				pNewNode = pNewNode->next;
			}
			return NewHead;
		}
		else
		{
			return NULL;
		}
    }
};