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/**
 * 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;
        map<RandomListNode*, RandomListNode*> nodeMap;
        
        RandomListNode *curHead = head;
        while (curHead != NULL) {
            nodeMap[curHead] = new RandomListNode(curHead->label);
            curHead = curHead->next;
        }
        
        curHead = head;
        while (curHead != NULL) {
            nodeMap[curHead]->next = curHead->next != NULL ? nodeMap[curHead->next] : NULL;
            nodeMap[curHead]->random = nodeMap[curHead->random];
            curHead = curHead->next;
        }

        return nodeMap[head];
    }
};