CodeNation arrived in our college premises in the end of July '15, to hire Summer Interns. We, at IIT(BHU), had already heard of the superb culture of CodeNation, and were super excited to get selected for the same.  CodeNation's Intern hiring criteria is one of the toughest and coolest of all, that i have encountered.  It all began with a written round on HackerRank. There were 4 questions, that were required to be solved in 1 and Half hour. The first question was Cakewalk, Second was based on 1-D DP, third one was based on Greedy and the last was 2-D DP. Then there were couple of interviews and finally an HR round. I managed to solve 2 and Half questions ( Half means some test cases of one question), and was selected for the interview process, along with some other batch mates. Now came the Interview rounds. Basically, the interviews were Skype based. In the first round, I came across an IITB Alumnus. Firstly he asked to describe me, and all the stuffs that i had done till then. Then he asked to describe in detail, about my project, and I described my Data Analysis Project, that I had done. Then he asked me a question: Given a Binary tree (To simplify one may assume complete), We had to reverse all the nodes on a particular level for every alternate level. (Note we have to make change in tree, and not just print them). I didn't know any standard algorithm, so I devised an elegant solution on my own. Some of my friends told me it could be done with Queue, However i used recursion. Later around the midnight on the same date, My 2nd round of interview was scheduled. Here I came across a team member of CodeNation, from Dubai HQ. This was one of the best experience for me till date. Then he asked me to write a code to solve dependencies of a software, install them first and then Install the software. I devised an O(n) solution through recursion (Brute Force). Finally he asked how to install multiple softwares at a time and present a code for the same .