Palindrome Linked List - ALawliet/algorithms GitHub Wiki
https://www.youtube.com/watch?v=yOzXms1J6Nk&ab_channel=NeetCode
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, val=0, next=None):
# self.val = val
# self.next = next
class Solution:
def isPalindrome(self, head: Optional[ListNode]) -> bool:
fast = head
slow = head
# find middle (slow)
while fast and fast.next:
fast = fast.next.next
slow = slow.next
# reverse second half (n=cn, cn=p, p=c, c=n)
prev = None
while slow: # cur
tmp = slow.next
slow.next = prev
prev = slow
slow = tmp
# check palindrome
left, right = head, prev
while right:
if left.val != right.val:
return False
left = left.next # ->
right = right.next # <-
return True