Array Squish (without using Ruby's defined method Array#flatten native method)

README.md

Array Squish

Array flatten without using Ruby's native method Array#flatten

Problem description

Write some code, that will flatten an array of arbitrarily nested arrays of integers into a flat array of integers. e.g. [[1,2,[3]],4] -> [1,2,3,4].

Solution

Create an array dinamically by pushing element inside only when the size of array (if present) is lower of equal to depth. Inside the class "ArrayFunctions" you will find a method called "squish" which will receive two parameters: array, depth.

  arr.each_with_object([]) do |element, flattened|
    flattened.push *(element.is_a?(Array) && n != nil && element.size <= n ? squish(element, n) : element)
  end

As you can see we will loop the array until we reach last element inside, and we will push elements on a temporary array only when the element has been "squished" by this i mean that the stop flag will be add elements that have no children (are not an array) or if they do add them only is depth allows it (element.size <= n).

##Source code Sample app and source code can be downloaded here

###Or keep reading to see this sample gist below

    |-- Gemfile
    |-- Gemfile.lock
    |-- Guardfile
    |-- Rakefile
    |-- README.md
    |-- example.rb
    |-- arrayfunctions.rb
    |-- arrayfunctions_unit_test.rb
            
  ###Use instructions
        #just require your helper class
        require './arrayfunctions'
        #there is no need to create an instance
        puts ArrayFunctions.squish([1])

  ###Run test instructions
      ruby arrayfunctions_test.rb

arrayfunctions.rb

#everything is better defined as a class
class ArrayFunctions

  def self.squish(arr, n = nil)
    begin
      arr.each_with_object([]) do |element, flattened|
        flattened.push *(element.is_a?(Array) && n != nil && element.size <= n ? squish(element, n) : element)
      end
    rescue
      #log or treat exception different
      #depending on your needs
      puts "Unexpected error: code ###"
    end
  end

end

arrayfunctions_unit_test.rb

require 'minitest/autorun'
require './arrayfunctions'

class Tests < MiniTest::Unit::TestCase

  #test with default example data provided on http://careers.citrusbyte.com/apply/tPTZOv/Experienced-Software-Developer
  def test_with_website_data
    array = [[1,2,[3]],4]
    #it should be 2
    assert_equal array.size, 2
    array = ArrayFunctions.squish(array, 1)
    #it should be increased by one
    assert_equal array.size, 4
  end

  #one level of nesting flatten
  def test_nested_2_level
    array = [1,[2, 3]]
    #it should be 2
    assert_equal array.size, 2
    array = ArrayFunctions.squish(array, 1)
    #it should be increased by one
    assert_equal array.size, 3
  end

  #two levels of nesting flatten
  def test_nested_3_levels
    array = [1,[2, 3, [4,5,6]]]
    #it should be 2
    assert_equal array.size, 2
    array = ArrayFunctions.squish(array, 3)
    #it should be increased by one
    assert_equal array.size, 6
  end
  
end

example.rb

require './arrayfunctions'

#not required to create an instance of ArrayFunctions
p ArrayFunctions.squish([[1,2,[3]],4],1) # [1, 2, [3], 4]
p ArrayFunctions.squish([1])         # [1]
p ArrayFunctions.squish([[1],2])     # [1, 2]
p ArrayFunctions.squish([[1,[2]]],1) # [1, [2]]

Gemfile

source 'https://rubygems.org'
#gems by groups, env

Guardfile

# A sample Guardfile
# More info at https://github.com/guard/guard#readme

guard :ruby do
  watch(%r{(.*)\.rb$})
end

Rakefile

require 'rake'
require 'rake/testtask'

Rake::TestTask.new do |t|
  t.pattern = '*.rb'
end

task :default => [:test]