/** * 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 boolean isPalindrome(ListNode head) { if (head.next == null) return true; // 1. 找到链表的中点 ListNode p1 = head; ListNode p2 = head; while (p2.next != null && p2.next.next != null){ p1 = p1.next; p2 = p2.next.next; } // 2. 反转链表 ListNode prev = p1; p1 = p1.next; prev.next = null; while (p1 != null){ ListNode tmp = p1.next; p1.next = prev; prev = p1; p1 = tmp; } // 3. 检查链表是否相同 p1 = prev; p2 = head; while (p1 != null && p2 != null){ if (p1.val != p2.val) return false; p1 = p1.next; p2 = p2.next; } return true; } }