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53

Palindrome Linked List

Difficulty: EASY
Avg. time to solve
20 min
Success Rate
90%

Problem Statement

You are given a singly Linked List of integers. Your task is to return true if the given singly linked list is a palindrome otherwise returns false.

For example:
The given linked list is 1 -> 2 -> 3 -> 2-> 1-> NULL.

It is a palindrome linked list because the given linked list has the same order of elements when traversed forwards and backward​.
Follow Up:
Can you solve the problem in O(N) time complexity and O(1) space complexity iteratively?
Input format :
The first line of input contains an integer 'T' representing the number of test cases or queries to be processed. Then the test case follows.

The only line of each test case contains the elements of the singly linked list separated by a single space and terminated by -1. Hence, -1 would never be a list element.
Output format :
For each test case, print “true” or “false” in a separate line.
Note :
You do not need to print anything, it has already been taken care of. Just implement the given function.
Constraints :
1 <= T <= 10
0 <= L <= 10^5
1 <= data <= 10^9 and data != -1

Where L is the number of nodes in the Linked List.

Time Limit: 1 sec
Sample Input 1 :
2
1 2 3 4 5 6 -1
1 2 1 -1
Sample Output 1 :
false
true
Explanation for sample 1:
For the first test case, it is not a palindrome because Linked List doesn't have the same order of elements when traversed forwards and backwards​.

For the second test case, it is a palindrome linked list because a Linked List has the same order of elements when traversed forwards and backwards​.
Sample Input 2 :
2
1 -1
1 10 45 10 1 -1
Sample Output 2 :
true
true
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