Skip to content
Programming101
Programming101

Learn everything about programming

  • Home
  • CS Subjects
    • IoT – Internet of Things
    • Digital Communication
    • Human Values
  • Programming Tutorials
    • C Programming
    • Data structures and Algorithms
  • HackerRank Solutions
    • HackerRank Algorithms Solutions
    • HackerRank C problems solutions
    • HackerRank C++ problems solutions
    • HackerRank Java problems solutions
    • HackerRank Python problems solutions
Programming101
Programming101

Learn everything about programming

HackerRank Ruby – Enumerable – reduce problem solution

YASH PAL, 31 July 2024

In this HackerRank Ruby – Enumerable – reduce problem solution A common scenario that arises when using a collection of any sort, is to get perform a single type of operation with all the elements and collect the result.

For example, a sum(array) function might wish to add all the elements passed as the array and return the result.

A generalized abstraction of same functionality is provided in Ruby in the name of reduce (inject is an alias). That is, these methods iterate over a collection and accumulate the value of an operation on elements in a base value using an operator and return that base value in the end.

Let’s take an example for better understanding.

>>> (5..10).inject(1) {|product, n| product * n }

=> 151200

In above example, we have the following elements: a base value 1, an enumerable (5..10), and a block with expressions instructing how to add the calculated value to base value (i.e., multiply the array element to product, where product is initialized with base value)

So the execution follows something like this:

# loop 1

n = 1

product = 1

return value = 1*1

# loop 2

n = 2

product = 1

return value = 1*2

n = 3

product = 2

return value = 2*3

..

As you can notice, the base value is continually updated as the expression loops through the element of container, thus returning the final value of base value as result.

Other examples,

>>> (5..10).reduce(1, :*)   # :* is shorthand for multiplication

=> 151200

Consider an arithmetico-geometric sequence where the nth term of the sequence is denoted by tn = n*n + 1, n >= 0. In this challenge, your task is to complete the sum method which takes an integer n and returns the sum to the n terms of the series.

HackerRank Ruby - Enumerable - reduce problem solution

Problem solution.

def sum_terms(n)
  # your code here
    nums = []
    (1).upto(n) do |i|
        nums << ((i*i)+1)
    end
    nums.reduce(0, :+)
end

Second solution.

def array_up_to(i)
    (1..i).to_a
end
def sum_terms(n)
    if n==0
        return 0 
    end
    t = array_up_to(n)
    t=t.map{|x| x**2+1}
    
    return t.inject{|sum,x| sum + x }
    
    
  # your code here
end

coding problems ruby

Post navigation

Previous post
Next post
  • HackerRank Separate the Numbers solution
  • How AI Is Revolutionizing Personalized Learning in Schools
  • GTA 5 is the Game of the Year for 2024 and 2025
  • Hackerrank Day 5 loops 30 days of code solution
  • Hackerrank Day 6 Lets Review 30 days of code solution
©2025 Programming101 | WordPress Theme by SuperbThemes
Programming101
Programming101

Learn everything about programming

  • Home
  • CS Subjects
    • IoT – Internet of Things
    • Digital Communication
    • Human Values
  • Programming Tutorials
    • C Programming
    • Data structures and Algorithms
  • HackerRank Solutions
    • HackerRank Algorithms Solutions
    • HackerRank C problems solutions
    • HackerRank C++ problems solutions
    • HackerRank Java problems solutions
    • HackerRank Python problems solutions