题目链接:https://www.acwing.com/problem/content/33/
题目如下:
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
//方法一:迭代
ListNode* reverseList(ListNode* head) {
ListNode* pre=NULL,*cur=head;
while(cur!=NULL){
ListNode* next=cur->next;//保存cur的下一个节点,因为接下来要改变cur-》next
cur->next=pre;//反转操作
pre=cur;//更新pre和cur指针
cur=next;
}
return pre;//pre是反转后的头节点
}
};
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* reverseList(ListNode* head) {
//方法二:递归
if(head==NULL||head->next==NULL) return head;//防止空链表及只有一个节点的链表
auto next=reverseList(head->next);
head->next->next=head;
head->next=NULL;
return next;
}
};