Given an array find the minimum difference between any pair.
Find the longest palindromic substring in a given string.
Round 2: Technical Interview
Find middle of Linked List: Given the head of a singly linked list, return the middle node of the linked list. If there are two middle nodes, return the second middle node.
Given an array of distinct integers, find if there are two pairs (a, b) and (c, d) such that a+b = c+d and a, b, c, and d are distinct elements. If there are multiple answers, then print any of them.