[leetcode 138]Copy List with Random Pointer

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本文介绍了一种解决带随机指针的链表深拷贝问题的算法，详细解释了如何通过哈希表实现每个节点的复制及复制后的随机指针连接。

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) {
        unordered_map<RandomListNode*, RandomListNode*> old2new;
        RandomListNode *old_cur = head;
        RandomListNode* dummy = new RandomListNode(-1);
        RandomListNode* new_cur = dummy;
        while (old_cur) {
            RandomListNode *newNode = new RandomListNode(old_cur->label);
            old2new[old_cur] =newNode;
            new_cur->next = newNode;
            new_cur = new_cur->next;
            old_cur = old_cur->next;
        }
        old_cur = head;
        while (old_cur) {
            old2new[old_cur]->random = old2new[old_cur->random];
            old_cur = old_cur->next;
        }
        return dummy->next;
    }
};