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Leetcode
Medium
Linked Lists
Stacks
Two Pointers
Amazon
Microsoft
Palindrome Linked List

Determine whether a singly linked list reads the same forward and backward.

Acceptance 100%
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Problem Statement

Given the head of a singly linked list, determine whether the sequence of node values forms a palindrome.

A list is a palindrome if reading the values from left to right gives the same result as reading them from right to left.

You should return true if the list is palindromic and false otherwise.

Input Format

  • A singly linked list is provided via its head node.
  • Each node contains an integer value.
  • The list may be empty.

Output Format

  • Return true if the linked list is a palindrome.
  • Otherwise, return false.

Constraints

  • The linked list can contain any integer values.
  • Aim for O(n)O(n) time.
  • Use O(1)O(1) extra space if possible.
Examples
Sample cases returned by the problem API.

Example 1

Input

head = [1,2,2,1]

Output

true

Explanation

The values read the same from both directions.

Example 2

Input

head = [1,2]

Output

false

Explanation

The forward order is [1,2], while the reverse order is [2,1].

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