[LeetCode] Copy List with Random Pointer

https://oj.leetcode.com/problems/copy-list-with-random-pointer/

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.

Analysis

Apparently, it’s not a difficult question to clone a linked list without an additional random pointer. For us, the trickier part, however, is to clone the random list node structure. My idea is using a HashTable.

Code

/** * Author : Acjx * Email : zhoujx0219@163.com */

/** * 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: /** * @param head: The head of linked list with a random pointer. * @return: A new head of a deep copy of the list. */ RandomListNode *copyRandomList(RandomListNode *head) { RandomListNode *dummyHead = new RandomListNode(0); RandomListNode *p = head, *q = dummyHead; unordered_map<RandomListNode *, RandomListNode *> map; while (p != NULL) { q->next = new RandomListNode(p->label); map.insert(make_pair(p, q->next)); p = p->next; q = q->next; } p = head; q = dummyHead; while (p != NULL) { q->next->random = map[p->random]; p = p->next; q = q->next; } return dummyHead->next; } };