Backend Developer

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?

You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to return the list of all pairs of elements such that each sum of elements of each pair equals 'S'.

Note:

Each pair should be sorted i.e the first value should be less than or equals to the second value. 

Return the list of pairs sorted in non-decreasing order of their first value. In case if two pairs have the same first value, the pair with a smaller second value should come first.

You have been given a sorted array/list 'arr' consisting of ‘n’ elements. You are also given an integer ‘k’.

Now the array is rotated at some pivot point unknown to you.

For example, if 'arr' = [ 1, 3, 5, 7, 8], then after rotating 'arr' at index 3, the array will be 'arr' = [7, 8, 1, 3, 5].

Now, your task is to find the index at which ‘k’ is present in 'arr'.

Note :

1. If ‘k’ is not present in 'arr', then print -1.
2. There are no duplicate elements present in 'arr'. 
3. 'arr' can be rotated only in the right direction.

Example:

Input: 'arr' = [12, 15, 18, 2, 4] , 'k' = 2

Output: 3

Explanation:
If 'arr' = [12, 15, 18, 2, 4] and 'k' = 2, then the position at which 'k' is present in the array is 3 (0-indexed).

Given a singly linked list of integers. Your task is to return the head of the reversed linked list.

For example:

The given linked list is 1 -> 2 -> 3 -> 4-> NULL. Then the reverse linked list is 4 -> 3 -> 2 -> 1 -> NULL and the head of the reversed linked list will be 4.

Follow Up :

Can you solve this problem in O(N) time and O(1) space complexity?

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