Showing posts from 2015

Setting up nginx + HHVM (hacklang) on OpenShift

I have recently moved my personal website from Google App Engine to OpenShift . I was looking at the list backend technologies supported by OpenShift and HHVM piqued my interest. I remembered how Facebook introduced a new language a few years ago and I never tried it out. So I decided to give it a try now. Fortunately, there is an OpenShift quickstart available for HHVM and we don't need to do any complex configuration to set it up. First of all, you need to sign up for OpenShift (it's free!). Now, that you have an OpenShift account, go ahead and create a new application. You will be shown a list of popular cartridges and quickstarts available. Select the HHVM quickstart. The next page will ask more details about your application like the sub-domain name, scaling options etc. Fill in the details as you wish and create the application. Now that your application is ready, you need a way to make changes to it. For that, you need to install rhc (OpenShift client tools) and mana

Introduction to tries through Facebook Hacker Cup 2015 Round 1 - Autocomplete

In the last week's post I discussed the solution to the problem "Homework" from Facebook Hacker Cup 2015 Round 1. This post is about the problem "Autocomplete" from the same round. You can  read the problem statement  available on the Facebook website. If you don't have a Facebook account, you can download problem statements from Codeforces Gym . I will re-state the problem in fewer lines. You have a new phone which has an auto-complete feature. But, it will complete your word only if there is there is no ambiguity on how the word should be completed. Formally, it will complete a word iff there is exactly one way to complete the word. It so happens that the phone's dictionary is empty by default. So, for the auto-complete feature to work, before typing a word you need to add that word to the dictionary. You need to send a message containing \(N\) words. What is the minimum number of characters must you type to send all \(N\) words? (Note that the

Problem discussion: Facebook Hacker Cup 2015 Round 1 - Homework

It's been a long time since I last wrote on this blog and a lot has happened since then. The most important of all is that my personal website is up at  and consequently this blog can now be accessed at . Also, you can now reach through email at . Let's get down to business now. The online part of Facebook Hacker Cup 2015 concluded recently and the top 25 contestants have been selected to compete in the onsite finals. The problem I am writing about in this post appeared in the Round 1 (there were 3 rounds). The title of the problem is "Homework" and here is the abridged statement: Given three integers \(A\), \(B\) and \(K\), find the number of integers in range \(\big[A, B\big] \) that have a "primacity" of \(K\). Primacity of a number \(N\) is defined as the number of distinct prime factors of \(N\). You have to process \(T\) such queries. The constraints are as follows: \(2 \le A \le B \le 10^