反转单链表

递归版

ListNode* reverseListRecursive(ListNode *head)
{
if(head == NULL || head->next == NULL)
return head;
ListNode *newHead = reverseListRecursive(head->next);
head->next->next = head;
head->next = NULL;
return newHead;
}

非递归版

ListNode* reverseList(ListNode *head)
{
if(head == NULL || head->next == NULL)
return head;
ListNode *newHead = NULL;
ListNode *p = head;
while (p != NULL)
{
ListNode *tmp = p;
p = p->next;
tmp->next = newHead;
newHead = tmp;
}
return newHead;
}