Given the head of a singly linked list, return true if it is a palindrome.
Example 1:
Input: head = [1,2,2,1]
Output: true
Example 2:
Input: head = [1,2]
Output: false
Constraints:
- The number of nodes in the list is in the range
[1, 105]. -
0 <= Node.val <= 9
Follow up: Could you do it in O(n) time and O(1) space?SOLUTION:
# 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:
curr = head
stack = []
while curr:
stack.append(curr.val)
curr = curr.next
curr = head
while curr:
if curr.val != stack.pop():
return False
curr = curr.next
return True
Top comments (0)