LeetCode 234. 回文链表

题目描述

🔥 234. 回文链表

image-20220917133914464

思路分析

  1. 获取链表的中间节点
  2. 反转链表的后半部分
  3. 比较

参考代码

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func isPalindrome(head *ListNode) bool {
	if head == nil || head.Next == nil {
		return true
	}
	slow, fast := head, head
	var pre *ListNode
	for fast != nil && fast.Next != nil {
		pre = slow
		slow = slow.Next
		fast = fast.Next.Next
	}
	pre.Next = nil
	l1, l2 := head, reverse(slow)
	for l1 != nil {
		if l1.Val != l2.Val {
			return false
		}
		l1 = l1.Next
		l2 = l2.Next
	}
	return true
}

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

🍏 点击查看 Java 题解

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class Solution {
    public boolean isPalindrome(ListNode head) {
        if (head == null || head.next == null) {
            return true;
        }
        ListNode slow = head, fast = head;
        while (fast != null && fast.next != null) {
            slow = slow.next;
            fast = fast.next.next;
        }

        ListNode pre = null, cur = slow;
        while (cur != null) {
            ListNode next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }

        ListNode p1 = head, p2 = pre;
        while (p2 != null) {
            if (p1.val != p2.val) {
                return false;
            }
            p1 = p1.next;
            p2 = p2.next;
        }
        return true;
    }
}

相似题目

题目 难度 题解
回文数 Easy  
验证回文串 Easy  
反转链表 Easy  
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