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：

 // http://www.careercup.com/question?id=5412018236424192
 #include <unordered_map>
 using namespace std;

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

 class Solution {
 public:
     RandomListNode *copyRandomList(RandomListNode *head) {
         // IMPORTANT: Please reset any member data you declared, as
         // the same Solution instance will be reused for each test case.
         int n;

         if(nullptr == head){
             return nullptr;
         }

         n = ;
         RandomListNode *ptr;

         ptr = head;
         while(ptr != nullptr){
             ++n;
             mri[ptr] = n;
             ptr = ptr->next;
         }

         RandomListNode *root, *tail;
         ptr = head;

         int i = ;
         tail = root = nullptr;
         while(ptr != nullptr){
             ++i;
             if (root == nullptr) {
                 root = tail = new RandomListNode(ptr->label);
             } else {
                 tail->next = new RandomListNode(ptr->label);
                 tail = tail->next;
             }
             mir[i] = tail;
             ptr = ptr->next;
         }

         RandomListNode *p1, *p2;

         p1 = head;
         p2 = root;
         while(p1 != nullptr){
             if(p1->random != nullptr){
                 p2->random = mir[mri[p1->random]];
             }
             p1 = p1->next;
             p2 = p2->next;
         }

         mir.clear();
         mri.clear();

         return root;
     }
 private:
     unordered_map<RandomListNode *, int> mri;
     unordered_map<int, RandomListNode *> mir;
 };