【LeetCode】206. Reverse Linked List

最新推荐文章于 2025-09-13 09:06:35 发布

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原文链接：http://www.cnblogs.com/yongh/p/9987088.html

文章标签：

#java #数据结构与算法

本文深入探讨了链表逆序的两种实现方式：迭代法与递归法，并提供了详细的Java代码示例。通过直观的解释和代码分析，帮助读者理解链表逆序背后的逻辑与技巧。

Difficulty:easy

More:【目录】LeetCode Java实现

Description

Reverse a singly linked list.

Example:

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

Follow up:

A linked list can be reversed either iteratively or recursively. Could you implement both?

Intuition

refer to 反转链表

pay attention : head.next=null

Solution

    /*recursively*/
    public ListNode reverseList(ListNode head) {
        ListNode newHead=reverse(null,head);
        return newHead;
    }
    
    private ListNode reverse(ListNode pre,ListNode cur){
        if(cur==null)
            return pre;
        ListNode next=cur.next;
        cur.next=pre;
        return reverse(cur,next);
    }
    
    /*iteratively*/
    public ListNode reverseList2(ListNode head) {
        ListNode pre = null;
        ListNode cur = head;
        while(cur!=null){
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
    }