LinkList6

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题目描述[原题链接][https://leetcode-cn.com/problems/reverse-linked-list/]

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

算法描述

​ 将整个链表进行反转，返回最后的结果，使用三个节点，进行循环迭代，转换指针的方向，直到链表尾部

C++代码

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class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        
        struct ListNode* prev = NULL;
        struct ListNode* curr = head;
        struct ListNode* next = NULL;
        
        while (curr) {
            next = curr->next;
            curr->next = prev;
            prev = curr;
            curr = next;
        }
        
        return prev;
    }
};

Java代码

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class Solution {
    public ListNode reverseList(ListNode head) {
        if(head==null||head.next==null)return head;
        ListNode prev = null;
        ListNode curr = head;
        ListNode next = null;
        while (curr!=null) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        
        return prev;
    }
}