/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode() : val(0), next(nullptr) {}
* ListNode(int x) : val(x), next(nullptr) {}
* ListNode(int x, ListNode *next) : val(x), next(next) {}
* };
*/
class Solution {
public:
ListNode* reverseList(ListNode* head) {
if (head == nullptr)
return head;
//快慢双指针
//直接一个一个结点的反转
ListNode* cur = NULL, *NEXT = head;
while (NEXT != NULL)
{
ListNode* tmp = NEXT->next;//tmp临时指针，存放未被反转的链表，防止丢失
NEXT->next = cur;
cur = NEXT;
NEXT = tmp;
}
return cur;
}
};
