IntelliJ productivity tips

Sep 18, 2017

This post is based on a talk on IntelliJ productivity and contains some tips and tricks I found handy in my everyday work.

You may disagree with me or find these recommendations useless for yourself, but I and some of my teammates have found out these tips have made us more efficient when dealing with lots of code in a big project.

  • say “no!” to tabs – that’s it – disable them. Forever. IntellJ has many ways to navigate the project, just check them out: Cmd+E, Cmd+Alt+← and Cmd+Alt+→

  • stop using mouse – just as with navigation in open files, IntelliJ offers awesome code navigation: want to go to the method definition? Cmd+B, want to find a file or class or method? Shift, Shift or Ctrl+Shift+N or Ctrl+N, want to move around in Project Manager? Cmd+1 (and then Esc to switch between editor and Manager)

  • use IntelliJ’s code intelligence – if you forgot what params method takes, use Cmp+P, if you want to find variable or class or method usage – use Alt+F7, use the power of “Refactor -> Extract Constant/Field” function

  • use action finder popup – that one can save you lot of time when you do not remember where the function needed is located or what key shortcut to use – Cmd+Shift+A is your friend

WARNING: lots of video/gifs under the cut!

Floyd-Warshall algorithm

Sep 4, 2017

The story behind this post

Recently I’ve received +10 karma on StackOverflow. I was curious for what question or answer and clicked to check this. It appeared to be a seven-year-old answer about a Floyd-Warshall algorithm. I was surprised both of my bad English back those days and the very small value the answer had. So I’ve revised it and here it is – the brand-new version!

The definitions

Let us have a graph, described by matrix D, where D[i][j] is the length of the edge (i -> j) (from graph’s vertex with index i to the vertex with index j).

Matrix D has the size of N * N, where N is a total number of vertices in a graph because we can reach the maximum of paths by connecting each graph’s vertex to each other.

Also, we’ll need matrix R, where we will store shortest paths (R[i][j] contains the index of a next vertex in the shortest path, starting at vertex i and ending at vertex j).

Matrix R has the same size as D.

The Floyd-Warshall algorithm performs these steps:

  1. initialize the matrix of all the paths between any two pairs of vertices in a graph with the edge’s end vertex (this is important since this value will be used for path reconstruction)

  2. for each pair of connected vertices (read: for each edge (u -> v)), u and v, find the vertex, which forms shortest path between them: if the vertex k defines two valid edges (u -> k) and (k -> v) (if they are present in the graph), which are together shorter than path (u -> v), then assume the shortest path between u and v lies through k; set the shortest pivot point in matrix R for edge (u -> v) to be the corresponding pivot point for edge (u -> k)

But how do we read the matrix D?

Easy way to understand algorithm complexity and big O notation

Aug 15, 2017


Some time ago I’ve published an article about bit O notation. I’ve mentioned its source but never published it. So here it is, the original article.

The article

Big O notation is the most widely used method which describes algorithm complexity - the execution time required or the space used in memory or in the disk by an algorithm. Often in exams or interviews, you will be asked some questions about algorithm complexity in the following form:

For an algorithm that uses a data structure of size n, what is the run-time complexity or space complexity of the algorithm? The answer to such questions often uses big O notations to describe the algorithm complexity, such as O(1), O(n), O(n^2) or O(log(n)).

My new hobby

Apr 9, 2017

I’ve got amused by how deep and well-designed are those old ASCII-art rogue-like games! So for the last couple of days I’ve spent numerous hours playing as a Necromancer Troll (Beat enemies! Eat enemies!) in ADOM and taking command of a dwarwish horde in Dwarf Fortress. Amazing level of detail! Most powerful graphics engine in the world (which is your own imagination)!

Gantt chart with D3.js

Apr 9, 2017

At work, I’ve had a task to implement a Gantt chart diagram to show dependencies and order of some… let’s say, milestones. Given this feature is in a very unstable beta in Google Charts, I thought to myself: “Why don’t I implement it on my own?”. And tried to recall my D3 knowledge.

I’ve also found a minimalistic, but helpful example / screenshot of some Gantt chart implementation:

The challenges I’ve faced were:

  1. order milestones on a timeline
  2. scale milestones to fit in a viewport
  3. create pretty connection lines
  4. center text inside each milestone

And since D3 is a data-driven library, I’ve used map/reduce where possible.

Here’s how the result looked like:

The full implementation code is under the cut.


Mar 13, 2017


Some time ago there was a game popular over there, called Entanglement:

There are a few implementations of this game under Android:

But there was no such game for iOS. And as I pursued my second M. Sc. degree, I have had a course “iOS development”, where we were learning to use Swift and iOS platform.

I decided to implement this game as my course project. In Swift. Originally the game was implemented in Swift 2 (there was no Swift 3 back those days).

And recently I decided to refactor the game a bit and update it to the most recent Swift version (which is Swift 3 at the moment of writing this post).

In this post I’ll describe some interesting decisions I made while creating this game.

libc.js: component interaction

Mar 12, 2017


Recently I’ve written a post about functional programming techniques, coming into the world of front-end and the library I crafted as an experiment. That library, libc.js was highly inspired by Elm and Mithril. But it suffered two major features:

  1. components were hardly able to be used in other components
  2. the interaction between components was nearly impossible (or, at least, not very transparent)

What’s hidden beneath the next version of the library?

Speeding-up algorithms with SSE

Feb 21, 2017

Have you ever asked anyone if assembly language might be useful nowadays? So, here’s the short answer: YES. When you know how your computer works (not a processor itself, but the whole thing - memory organization, math co-processor and others), you may optimize your code while writing it. In this short article, I shall try to show you some use cases of optimizations, which you may incorporate with the usage of low-level programming.

Recently I was reading through my old posts and found out there is a gap in the article about SSE - the post did not cover some of the implementation caveats. I decided to fulfill this and re-publish a new version.

Functional web

Feb 18, 2017

In last couple of years the functional programming paradigm became very popular. A huge amount of libraries, tools, tutorials and blog posts appeared. Although the paradigm itself is rather old (lambda calculus was developed around 1930 and the Lisp language was introduced in 1950), its popularity blew up rapidly somewhere in 2014-2016 and that’s what is happening right now. Probably one of the most powerful influencers, giving FP (functional programming) that thrust is web development. Since Facebook introduced React, the community started incorporating many things from FP with React - including Redux and Immutable.js. But there are much more interesting things which were invented on this wave of FP popularity. One of them is Elm.

This is a story how I implemented invented yet another web framework wheel.

Clojure guards

Dec 21, 2016

Once I wanted to have something like a pretty “match” operator from Scala, but in Clojure. And hence there are no default options for it in Clojure out of the box, here are some alternatives I’ve found in the Internet.