Hi there! The problem for today required me to find the quartiles of set of data values. The concept is actually new to me but, once I learned it, it resembled a lot the median of a data set. Actually, the second quartile Q2Q_2 is the median itself, while the other two quartiles, Q1Q_1 and Q2Q_2, are basically medians of sub datasets divided around the second quartile. The three quartiles divide the data in four regions instead of two regions using only the median. ...

Hi there! Well, the 30 days of code from HackerRank had some challenges that didn’t allow me to use Go and this is one of them. The idea is to create a custom exception and throw it. My choice of language was C++ and the solution is given below. Notice that not all code is mine, the IO handling was given by HackerRank (probably to force me use a class Calculator and an exception haha). ...

Hi there! Today’s problem is quite simple. The challenge is to compute the weighted mean given two arrays. The first input is NN, the number of elements of each array, and then the first array is given and then the second whose components are the weights. My solution is given below. package main import "fmt" func main() { N := 0 fmt.Scanf("%d", &N) a := make([]float64, N) b := make([]float64, N) for i := 0; i < N; i++ { fmt.Scanf("%f", &a[i]) } for i := 0; i < N; i++ { fmt.Scanf("%f", &b[i]) } numerator := 0.0 denominator := 0.0 for i := 0; i < N; i++ { numerator += a[i] * b[i] denominator += b[i] } mean := numerator / denominator fmt.Printf("%.1f\n", mean) } The only problem I had was that I forgot to read the arrays initially 😆. The rest of the code was quite easy given what I learned so far. I made use of type inference in Go which is quite nice.

This post is a little bit different from the last ones. Days 1-12 followed more or less strictly what HackerRank 30 days of code Tutorial had, but starting on day 13 there was a series of challenges that didn’t allow me to use Go. They are more specific to object-oriented languages like C++ and Java. As Go doesn’t have all the constructions these languages allow, like abstract classes, at least not without a workaround, I decided to take other challenges on HackerRank. The one for today is about statistics and I will introduce some of the concepts before showing the code solution. ...

Inheritance is a nice concept that object-oriented languages have. It is basically the ability for one type, many times called a class or even a struct depending on the language, to inherit the behaviour of another type. HackerRank doesn’t allow me, at least at the moment this post is being written, to submit code in Go for this challenge of inheritance. It seems like Go doesn’t support inheritance, though there are some workarounds that let us mimic the behaviour. The code below is what I tested to mimic the behaviour of a Student class that inherits from the Person class. The Student class has a different printPerson method that calls its super method (the method of the parents class) and it also inherits the sayHello function which is just called by the Student instance object. ...

Hi there! The challenge of today confused me a little in their definition, but they had a good example so it was not hard to get it. Basically I had to read a 6×66 \times 6 matrix and iterate over it summing a pattern of elements like abc d efg that is called an hourglass. So, I just had to iterate through an array and sum 7 elements of it for each iteration. My solution is below. ...

Archiving and compressing are two different concepts. Archiving is basically collecting files in a single package and a popular tool for that is called tar. Compressing is actually reducing file size by means of an algorithm and popular ones include bzip2 and gzip. I will talk about those, but first I would like to talk about another tool for creating archives: cpio. cpio The cpio command can be used to create a backup of the /home/ directory for instance: ...

This post is a collection of commands basically, I hope it works a reference for me and other people who pass by. To delete users, we have deluser and userdel. For me, it was really weird learning that we have two commands with similar names that basically do the same thing. I present some examples below. # removes user and home directory $ deluser -r user $ userdel user # remover user from group $ deluser user group # deleting a group $ deluser --group group Creating or deleting groups, adding a user to them or changing primary group: ...

When a system administrator wants see when a user last changed a password or wants to force a user to change it, there is a really nice command to come to the rescue: chage. I created a user called aluno and I started to check for its information: $ sudo chage -l aluno Last password change : Sep 16, 2016 Password expires : never Password inactive : never Account expires : never Minimum number of days between password change : 0 Maximum number of days between password change : 99999 Number of days of warning before password expires : 7 As we see, the user password was last changed on Sep 16, 2016 and it never expires nor gets inactive. This can be easily changed by using the command chage -M number_of_days and then checking the user info again: ...

The challenge for today is interesting, but I keep wondering if I could do it more efficiently. Let me know in the comments if you have any suggestion after reading my solution. The problem is counting the maximum number of consecutive binary ones in an integer. It is easier to understand with an example: Consider the number 25 represented in base 10 Its representation in binary is 11001 The max number of consecutive ones we can see is 2 What I did was shifting to the right and checking the least significant bit until every single bit of it was checked. The solution is available below. ...