力扣-剑指 Offer 24. 反转链表（C++）- 反转链表+递归_反转链表c++实现递归

题目链接：https://leetcode-cn.com/problems/fan-zhuan-lian-biao-lcof/
题目如下：

解一：反转链表

/**
 * 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) {
        ListNode* pre=NULL,*cur=head;

        while(cur!=NULL){
            ListNode* temp=cur->next;
            cur->next=pre;
            pre=cur;cur=temp;
        }
        
        return pre;
    }
};
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解二：递归
思路：

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

        head->next->next=head;
        head->next=NULL;//方便下次反转

        return newHead;//永远是返回后的头节点
    }
};
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