LeetCode 206. Reverse Linked List-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_31361913/article/details/106331350

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。通过具体代码示例，详细解释了每种方法的工作原理及其实现过程。对于理解链表数据结构及其操作，本文提供了宝贵的资源。

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这是一道很基本的题目，有Iterative和Recursive两种解法，我们最好都需要熟悉。

Iterative solution

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        // Initialization
        ListNode prev = null; 
        ListNode curr = head;
        while(curr != null){
            ListNode next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        // Do not forget to return the new head reference at the end!
        return prev;
    }
}

Recursive solution

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        // Base case
        if(head == null || head.next == null){
            return head;
        }
        // Keep the new head of the reversed linked list
        ListNode newHead = reverseList(head.next);
        head.next.next = head;
        head.next = null;
        return newHead;
    }
}