Ruby Partial Applications – HackerRank Solution

In this post, we will solve Ruby Partial Applications HackerRank Solution. This problem (Ruby Partial Applications) is a part of HackerRank Ruby series.

Problem

In Partial Application, we create a lambda that takes a parameter and returns a lambda that does something with it.

Example:

multiply_function = -> (number) do
   -> (another_number) do
       number * another_number
   end
end

doubler = multiply_function.(2)
tripler = multiply_function.(3)

puts doubler.(4)
puts tripler.(4)

In the above example, the lambda will take number as a parameter, and return a lambda. When you call this lambda with another_number, it will return the product of the two.

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Task

You are given a partially complete code. Your task is to fill in the blanks (_______).

Here, combination is a variable that stores a partial application which computes combination ⁿC_r.

Solution – Ruby Partial Applications – HackerRank Solution

combination = -> (n) do
        -> (r) do
        # https://en.wikipedia.org/wiki/Combination
        (n-r+1..n).inject(:*) / (1..r).inject(:*)
    end
end

n = gets.to_i
r = gets.to_i
nCr = combination.(n)
puts nCr.(r)

Note: This problem (Ruby Partial Applications) is generated by HackerRank but the solution is provided by CodingBroz. This tutorial is only for Educational and Learning purpose.