LeetCode【138】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.

看上去比较复杂，实际上也比普通的链表题复杂。两个思路，一个用hash表，存储旧地址和新地址，然后对应一一copy；第二个思路，就和剑指offer里面提到的那样，在每个节点后创建一个副本，假设为copy，则在拷贝random指针时相对简单了。copy->random等于源节点的random指针的next节点。实现如下，已AC：

RandomListNode *copyRandomList(RandomListNode *head) {
        if(!head)
            return head;
        // head is not NULL
        RandomListNode* h=head;
        //copy nodes and next pointers;
        while(h)
        {
            RandomListNode* copy = new RandomListNode(h->label);
            copy->next = h->next;
            h->next = copy;
            h=copy->next;
        }
        
        //copy random pointers
        h=head;
        while(h)
        {
            if(h->random)
                h->next->random = h->random->next;
            h=h->next->next;
        }
        //split
        h=head;
        RandomListNode* newHead=head->next;
        while(h)
        {   
            RandomListNode* newH= h->next;
            h->next = newH->next;
            h=newH->next;
            if(h)
                newH->next = h->next;
            else
                newH->next = h;
        }
        return newHead;
    }