[LeetCode] Copy List with Random Pointer

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.
剑指OFFER上的题，中间 head->random 原来有可能是NULL,所以要添加一个判断，很坑。

/**
* 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:
RandomListNode *copyRandomList(RandomListNode *head) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(!head)
return NULL;
cloneList(head);
cloneRandomPtr(head);
return removeClone(head);
}
void cloneList(RandomListNode* head)
{
while(head)
{
RandomListNode* toAdd=new RandomListNode(head->label);
RandomListNode* pNext=head->next;
toAdd->next=pNext;
head->next=toAdd;
head=pNext;
}
}
void cloneRandomPtr(RandomListNode* head)
{
while(head)
{
if(head->random)
head->next->random=head->random->next;
head=head->next->next;
}
}
RandomListNode* removeClone(RandomListNode* head)
{
RandomListNode guard(-1);
RandomListNode* tail=&guard;
while(head)
{
tail->next=head->next;
tail=tail->next;
head->next=head->next->next;
head=head->next;
}
return guard.next;
}
};