Given a linked list, reverse the direction of nodes in the list.
Given a linked list, check if it has a loop. If yes, remove the loop.
Given an array of integers, find the length of the longest subarray whose sum is 0.
Given a binary tree, connect the sibling nodes at each level.
Given pre-order & in-order traversal of a binary tree, construct the tree.
Given a binary tree, print the cousins of the given node.
Given a sorted array of integers rotated k times, check if given key is present in it?