연결 리스트¶

from typing import List 

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next        

node_2 = ListNode(2)
node_1 = ListNode(1, node_2)

node_6 = ListNode(1)
node_5 = ListNode(2, node_6)
node_4 = ListNode(2, node_5)
node_3 = ListNode(1, node_4)

def isPalindrome(head: ListNode) -> bool:
    checker = []

    cur = head
    while cur:
        checker.append(cur.val)
        cur = cur.next
    
    return checker == checker[::-1]

def isPalindrome(head: ListNode) -> bool:
    q = []
    
    if not head:
        return True
    
    node = head
    while node is not None:
        q.append(node.val)
        node = node.next
        
    while len(q) > 1:
        if q.pop(0) != q.pop():
            return False
        
    return True

import collections

def isPalindrome(head: ListNode) -> bool:
    q = collections.deque()
    
    if not head:
        return True
    
    node = head
    while node is not None:
        q.append(node.val)
        node = node.next
        
    while len(q) > 1:
        if q.popleft() != q.pop():
            return False
        
    return True

def isPalindrome(head: ListNode) -> bool:
    rev = None
    slow = fast = head
    
    while fast and fast.next:
        fast = fast.next.next
        rev, rev.next, slow = slow, rev, slow.next
    if fast:
        slow = slow.next
    
    while rev and rev.val == slow.val:
        slow, rev = slow.next, rev.next
    return not rev