给你一个单链表的头节点 head ,请你判断该链表是否为回文链表。如果是,返回 true ;否则,返回 false 。
示例 1:
输入:head = [1,2,2,1]
输出:true
示例 2:
输入:head = [1,2]
输出:false
提示:
链表中节点数目在范围[1, 105] 内
0 <= Node.val <= 9
题解:
/**
* 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 == null || head.next == null) {
return true;
}
List<Integer> result = new ArrayList<>();
while (head != null) {
result.add(head.val);
head = head.next;
}
int slow = 0;
int fast = result.size()-1;
while (slow <= fast) {
if (result.get(slow) != result.get(fast)) {
return false;
}
slow++;
fast--;
}
return true;
}
}