[Python] linked list의 runner 기법

# Definition for singly-linked list.
class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None


class Solution:
    def isPalindrome(self, head: ListNode) -> bool:
        rev = None
        slow = fast = head
        # 런너를 이용해 역순 연결 리스트 구성
        while fast and fast.next:
            fast = fast.next.next
            rev, rev.next, slow = slow, rev, slow.next
        if fast:
            slow = slow.next

        # 팰린드롬 여부 확인
        while rev and rev.val == slow.val:
            slow, rev = slow.next, rev.next
        return not rev

 

[출처]

https://github.com/onlybooks/algorithm-interview/blob/master/3-linear-data-structures/ch08/13-4.py