逆转链表 Reverse Linked List

迭代方法 Iterative Method

Node * reverse( Node * ptr )
{
    Node * next;
    Node * previous = NULL;
    while(ptr != NULL) {
        next = ptr->next;
        ptr->next = previous;
        previous = ptr;
        ptr = next;
    }
    return previous;
}

递归方法 Recursive Method

Node* reverse(Node *ptr)
{
	if(ptr->next == NULL)
		return ptr; //最右结点会一直传回到最外层
	Node *q = p->next;
	Node *head = reverse(q);
	q->next = ptr; //反向接回
	ptr->next = NULL;
	return head;
}