力扣206题:反转链表
/**
* 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 (nullptr == head) return head;
ListNode* cur = head;
ListNode* pre = nullptr;
ListNode* next = head->next;
while (cur != nullptr && next != nullptr) {
cur->next = pre;
pre = cur;
cur = next;
next = cur->next;
}
cur->next = pre;
return cur;
}
};