LeetCode: 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.
地址：https://oj.leetcode.com/problems/copy-list-with-random-pointer/
算法：将已经复制的节点存储在map里面。如果当前遍历到的节点在map里，则直接取出来；若不再map里则复制节点，并将节点存储在map里。代码:
1 /**
2 * Definition for singly-linked list with a random pointer.
3 * struct RandomListNode {
4 * int label;
5 * RandomListNode *next, *random;
6 * RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
7 * };
8 */
9 class Solution {
10 public:
11 RandomListNode *copyRandomList(RandomListNode *head) {
12 RandomListNode *p = head;
13 RandomListNode *new_head = NULL;
14 map<int, RandomListNode*> hash_table;
15 RandomListNode *new_p;
16 int label, r_label;
17 while(p){
18 label = p->label;
19 if(hash_table.find(label) == hash_table.end()){
20 RandomListNode * temp_p = new RandomListNode(label);
21 hash_table[label] = temp_p;
22 }
23 if(!new_head){
24 new_head = hash_table[label];
25 new_p = new_head;
26 }else{
27 new_p->next = hash_table[label];
28 new_p = new_p->next;
29 }
30 if(p->random){
31 r_label = p->random->label;
32 if(hash_table.find(r_label) == hash_table.end()){
33 RandomListNode *temp_p = new RandomListNode(r_label);
34 hash_table[r_label] = temp_p;
35 }
36 new_p->random = hash_table[r_label];
37 }
38 p = p->next;
39 }
40 return new_head;
41 }
42 };
