## Get number of common divisors in OCaml

Hi, everyone! In this challenge I used OCaml sets again. The goal was to get the number of common divisors for each pair of numbers in the test cases. The first function I wrote was to define a limit until when I would be checking if the number was divisible or not: (* Need to check divisors just up to sqrt x *) let max x = Int.of_float (sqrt x) |> (+) 1;; After that, I wrote a function to get the number of common divisors of a single number n....

March 28, 2017 · 3 min

## Dedup chars in a string using OCaml

Hi there! The goal of this challenge is to remove all duplicate chars in a string. The following input/output will explain it by itself: # input abcabczabczabc # output abcz I tried to write the functions to explode and implode from what I remembered, but in the end I had to take another look at their code here. Those were auxiliary functions to help me to write remove_all_dups. open Core.Std (* string -> char list *) let explode str = let len = String....

March 27, 2017 · 2 min

## Mingle strings in OCaml

Hi there! The problem that I solved this time was a little cumbersome initially, cause even though I knew well how to iterate over lists, I had no idea how to iterate over strings. The solution I found was inspired in the functions to explode and implode strings . These functions use the string indices to explode the string, creating a char list, or implode a char list, creating a string....

March 26, 2017 · 2 min

## List Replication

Hi there! The idea of this problem is just to read some numbers from stdin and replicate them, but using lists. The input would be like this: 3 // # of repetitions 1 // first number ... 2 3 4 // end of input, last number Then the output would be a list with each number repeated the amount of times given. For the case above, it would show “1” three times, “2” three times and so on, each element on a different line....

March 24, 2017 · 2 min

## Hello World printing in OCaml

Another simple problem from HackerRank is to print Hello World multiple times in a functional language. Well, I am using OCaml and I suppose I should avoid loops. The way I solved it is the following: open Core.Std let n = read_int ();; let rec print_hello n = if n > 0 then begin printf "Hello World\n"; print_hello (n-1); end else ();; print_hello n Problems I had: I lost some some time to discover the ;; was required to make it compile properly....

March 24, 2017 · 1 min

## Compare Triplets in OCaml

Hi there! It has been a while since I played with OCaml, so I am solving a simple problem from HackerRank. The problem says the following “Alice and Bob each created one problem for HackerRank. A reviewer rates the two challenges, awarding points on a scale from 1 to 100 for three categories: problem clarity, originality, and difficulty”. For each category, we must check who had a greater score and give a point to that person for each category....

March 24, 2017 · 3 min

## 30 days of code in Go: Day 21 - Extra Long Factorials

One of the big limitations of simple number data types is the maximum number they can hold. A 64 bit unsigned long can hold up to the number $2^{64}-1$. This is a pretty huge number, but if you try to compute the factorial of a number like $25!$, it is not enough. The good news is that there are software libraries that allow us to surpass this limitation. The bad is that the computations take longer....

October 12, 2016 · 2 min

## 30 days of code in Go: Day 19 - Binomial Distribution II

Hi there! Today’s problem is very similar to the last day, again using a binomial distribution. Question Given that 12% of the pistons of a manufacture are rejected because of incorrect sizing, what is the probability of batch of 10 pistons contain No more than two rejects? At least two rejects? Again, very similar. Now the probability of success for the Bernoulli trial is of the chance of the piston being reject, the same as being incorrectly sized....

October 6, 2016 · 2 min

## 30 days of code in Go: Day 18 - Binomial Distribution I

Hi there! Today’s challenge from HackerRank was a little more involved. The challenge is Given the ratio $1.09 : 1$ of boys to girls for babies born in a certain country, what is the proportion of families with exactly 6 children that will have at least 3 boys?. Before actually solving that, it is important to understand a Bernoulli trial and also the Binomial Distribution. Bernoulli trial According to Wikipedia, a Bernoulli trial is a random experiment with exactly two possible outcomes, “success” and “failure”, in which the probability of success is the same every time the experiment is conducted....

October 5, 2016 · 2 min

## 30 days of code in Go: Day 17 - Standard Deviation

Hi there! Today’s challenge was to compute standard deviation of an array of data given the formula $$\sigma = \sqrt{\frac{\sum_{i=0}^{N-1} (x_i - \mu)^2}{N}},$$ where $$\mu = \frac{\sum_{i=0}^{N-1} x_i}{N}.$$ The first input to the program is N and then N integers are fed to the program in sequence. My solution is given below. package main import ( "fmt" "math" ) func mean(a []int) float64 { n := float64(len(a)) sum := 0.0 for i := 0; i < len(a); i++ { sum += float64(a[i]) } return sum / n } func sigma(a []int) float64 { mu := mean(a) sum := 0....

October 4, 2016 · 2 min