题目
请判断一个链表是否为回文链表。
示例 1:
示例 2:
进阶:
你能否用 O(n) 时间复杂度和 O(1) 空间复杂度解决此题?
Related Topics
解答
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class Solution { public boolean isPalindrome(ListNode head) { if(head == null || head.next == null) return true;
int length = 0;
ListNode previous = head; while(previous != null){ length++; previous = previous.next; }
int[] arr = new int[length]; int index= 0; while(head != null){ arr[index] = head.val; index++; head = head.next; }
int after = arr.length / 2; int before = after - 1;
if(arr.length % 2 == 1){ after++; }
while(before >= 0 || after < arr.length){ if(arr[before] == arr[after]){ before--; after++; }else{ return false; } }
return true; }
}
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