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Chaos Ajax - is your application ready to fail?

· 3 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

You are creating an application that shows data to the user - doesn't matter if he is searching for some specific thing or he is only listing everything you have. What happens if the server responds with empty array? Or with error? Will your application show only empty space or an error message?

Write good git commit message

· 4 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

For a long time I didn't know that even writing commit message can have its own "best practices". When I got in touch with git for the first time, this part was described with words like "...and here you can write something short about what's going on in the commit".

Do (not?) write comments

· 2 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

We all know a lot of jokes about comments and why not to write them. Even many articles suggest not to write comments. Why is that so?

Node Version Manager and failing certificate verification

· One min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

In my current job, we have some kind of network settings ( or better proxy settings ) that from time to time cause problems with certificate verification.

Google Code Jam 2017: Tidy Numbers

· 4 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

Tatiana likes to keep things tidy. Her toys are sorted from smallest to largest, her pencils are sorted from shortest to longest and her computers from oldest to newest. One day, when practicing her counting skills, she noticed that some integers, when written in base 10 with no leading zeroes, have their digits sorted in non-decreasing order. Some examples of this are 8, 123, 555, and 224488. She decided to call these numbers tidy. Numbers that do not have this property, like 20, 321, 495 and 999990, are not tidy.

She just finished counting all positive integers in ascending order from 1 to N. What was the last tidy number she counted?

Introduction to Sequelize ORM

· 8 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

This is about the basic usage of Sequelize ORM – how to create migrations, models, seeders and how to get the data from the database. Everything is explained on an example project, which you can find on GitHub.

Lexicographical permutations

· 4 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

The solution for Bigger is Greater challenge on HackerRank, or how to generate next lexicographically greater string. Problem description, algorithm steps and complete source code to solve this challenge.

Google Code Jam 2017: Oversized Pancake Flipper

· 5 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

Last year, the Infinite House of Pancakes introduced a new kind of pancake. It has a happy face made of chocolate chips on one side (the “happy side”), and nothing on the other side (the “blank side”).

You are the head cook on duty. The pancakes are cooked in a single row over a hot surface. As part of its infinite efforts to maximize efficiency, the House has recently given you an oversized pancake flipper that flips exactly K consecutive pancakes. That is, in that range of K pancakes, it changes every happy-side pancake to a blank-side pancake, and vice versa; it does not change the left-to-right order of those pancakes.

You cannot flip fewer than K pancakes at a time with the flipper, even at the ends of the row (since there are raised borders on both sides of the cooking surface). For example, you can flip the first K pancakes, but not the first K – 1 pancakes.

Your apprentice cook, who is still learning the job, just used the old-fashioned single-pancake flipper to flip some individual pancakes and then ran to the restroom with it, right before the time when customers come to visit the kitchen. You only have the oversized pancake flipper left, and you need to use it quickly to leave all the cooking pancakes happy side up, so that the customers leave feeling happy with their visit.

Given the current state of the pancakes, calculate the minimum number of uses of the oversized pancake flipper needed to leave all pancakes happy side up, or state that there is no way to do it.

Prime numbers

· 7 min read
Matej Jelluš
Tech leader and IT nerd who is constantly trying new things, sharing his experiences and still enjoys writing code in his free time. Currently looking for new challenges and opportunities.

With this post I want to begin a series of posts about general algorithms. It is not an accident I started with the prime numbers. This is basic problem to solve when you are starting with programming. And one more reason – I was curious how RSA algorithm works and the important part of the algorithm is to generate two random big prime numbers.

Loading images and caching them with Fresco in Android

· 5 min read

I am working for a Start Up project – DiagramArt, where we needed to create Android application which : load list of diagrams from API, show these diagrams to the user and some other stuff of course. The list consists from a preview picture, diagram’s title and its description. There is no problem to load and show these data, the problem was in the preview picture.