Hackerrank

Hi there! Today’s challenge is quite similar to the last one. Again, there are quartiles, but the input is a little different and the output is the interquartile range: Q3−Q1Q_3 - Q_1. The first input is nn followed by an array XX of size nn with our data, but the frequencies of each point are included in another array of nn elements, FF, that is the next input. After reading this we need to construct the actual data array SS. My solution is below. ...

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. ...

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. ...

Hi there! Here I am coding again. For those of you readers who may not know what recursion is, I have a brief explanation: a function is called a recursive function when it calls itself. A very nice example is the factorial, which is also what I am going to code today. For the factorial of NN, f(N)f(N), we can state that f(N)=N×f(N−1)f(N) = N\times f(N-1). What we see is that the function is represented by itself, but with other argument and it can keep this going up to a certain point for which we know the answer like f(1)=f(0)=1f(1)=f(0)=1. Given this introduction, I will code. ...

Hi there! The task of today will be coding a phone book. The program reads an integer NN that represents the number of people in the phone book. After that, it reads the NN entries from standard output and generates the dictionary/map. For newbies: dictionaries are the same as maps. Java usually calls the structure with (key, value) pairs as a map, while Python calls it a dictionary. After having the phone book generated, the program will read an unknown number of names. The fact that we can query as many names as we want means that the program needs to check for an end of file before leaving, which is basically trying to read until the user cancels the program. Well, other options would be typing a special quit command, but that’s not the case for this problem. ...