[LeetCode] Copy List with Random Pointe
题目的关键是要让新链表和原有链表发送关联，可以通过这种关联来设置新链表的random pointer
思路：将新链表的元素插入到原有链表元素的后面，如下图所示，就可以根据原有链表的radom->next 就是新链表的random指针
所以分3步骤：
1 新元素插入
2 设置新链表的random
3 拆分大链表，回复old link 和new link
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 10 class Solution { 11 public: 12 RandomListNode *copyRandomList(RandomListNode *head) { 13 14 RandomListNode* pOld = head; 15 RandomListNode* pNew = NULL; 16 RandomListNode* pRes = NULL; 17 18 if(head == NULL) return NULL; 19 20 // insert every new node after old new node 21 while(pOld) 22 { 23 pNew = new RandomListNode(pOld->label); 24 if(pOld == head) pRes = pNew; 25 pNew->next = pOld->next; 26 pOld->next = pNew; 27 pOld = pNew->next; 28 } 29 30 31 pOld = head; 32 // constrct new's random pointer 33 while(pOld) 34 { 35 pNew = pOld->next; 36 if(pOld->random == NULL) 37 pNew->random == NULL; 38 else 39 pNew->random = pOld->random->next; 40 pOld = pNew->next; 41 } 42 43 44 // recover old's and new's next pointer 45 //恢复old list 和new list 46 47 pOld = head; 48 49 while(pOld) 50 { 51 pNew = pOld->next; 52 if(pNew == NULL) 53 pOld->next = NULL; 54 else 55 pOld->next = pNew->next; 56 pOld = pNew; 57 } 58 59 return pRes; 60 } 61 };
