LeetCode 206. 反转链表

题目描述

🔥 206. 反转链表

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思路分析

  1. 头插法
  2. 递归

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参考代码

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func reverseList(head *ListNode) *ListNode {
	if head == nil || head.Next == nil {
		return head
	}
	cur := head
	var pre *ListNode
	for cur != nil {
		next := cur.Next
		cur.Next = pre
		pre = cur
		cur = next
	}
	return pre
}

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func reverseList(head *ListNode) *ListNode {
	if head == nil || head.Next == nil {
		return head
	}
	newHead := reverseList(head.Next)
	head.Next.Next = head
	head.Next = nil
	return newHead
}

🍏 点击查看 Java 题解(一)

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

🍏 点击查看 Java 题解(二)

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public 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;
        return newHead;
    }
}

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