234. Palindrome Linked List

 

Example 1:

Input: head = [1,2,2,1]
Output: true

Example 2:

Input: head = [1,2]
Output: false

public boolean isPalindrome(ListNode head) {
    ListNode mid = getMid(head);
    ListNode headSecond = reverseList(mid);

    while(head != null && headSecond != null){
        if(head.val != headSecond.val){
            return false;
        }
        head = head.next;
        headSecond = headSecond.next;
    }
    return true;
}

public ListNode getMid(ListNode head){
    ListNode slow = head;
    ListNode fast = head;

    while(fast!= null && fast.next != null){
        slow = slow.next;
        fast = fast.next.next;
    }

    return slow;
}

public ListNode reverseList(ListNode node){
    
  // 反转链表部分可参考 反转链表
}