Careercup - Facebook面试题 - 5412018236424192

2014-05-01 01:32

题目链接

原题：

Given a linked list where apart from the next pointer, every node also has a pointer named random which can point to any other node in the linked list. Make a copy of the linked list.

题目：给定一个单链表，每个链表除了next指针以外，还有一个random指针，随机地指向nullptr或者链表中的某个节点。请设计算法完成一份链表的硬拷贝。

解法：Leetcode上有相关题目，请看题解LeetCode - Copy List with Random Pointer。

代码：

 1 // http://www.careercup.com/question?id=5412018236424192

 2 #include <unordered_map>

 3 using namespace std;

 4 

 5 struct RandomListNode {

 6     int label;

 7     RandomListNode *next, *random;

 8     RandomListNode(int x) : label(x), next(NULL), random(NULL) {};

 9 };

10 

11 class Solution {

12 public:

13     RandomListNode *copyRandomList(RandomListNode *head) {

14         // IMPORTANT: Please reset any member data you declared, as

15         // the same Solution instance will be reused for each test case.

16         int n;

17         

18         if(nullptr == head){

19             return nullptr;

20         }

21         

22         n = 0;

23         RandomListNode *ptr;

24         

25         ptr = head;

26         while(ptr != nullptr){

27             ++n;

28             mri[ptr] = n;

29             ptr = ptr->next;

30         }

31         

32         RandomListNode *root, *tail;

33         ptr = head;

34         

35         int i = 0;

36         tail = root = nullptr;

37         while(ptr != nullptr){

38             ++i;

39             if (root == nullptr) {

40                 root = tail = new RandomListNode(ptr->label);

41             } else {

42                 tail->next = new RandomListNode(ptr->label);

43                 tail = tail->next;

44             }

45             mir[i] = tail;

46             ptr = ptr->next;

47         }

48         

49         RandomListNode *p1, *p2;

50         

51         p1 = head;

52         p2 = root;

53         while(p1 != nullptr){

54             if(p1->random != nullptr){

55                 p2->random = mir[mri[p1->random]];

56             }

57             p1 = p1->next;

58             p2 = p2->next;

59         }

60         

61         mir.clear();

62         mri.clear();

63         

64         return root;

65     }

66 private:

67     unordered_map<RandomListNode *, int> mri;

68     unordered_map<int, RandomListNode *> mir;

69 };