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w1zeman1p's solution

to Pythagorean Triplet in the Ruby Track

Published at Feb 18 2019 · 0 comments
Instructions
Test suite
Solution

A Pythagorean triplet is a set of three natural numbers, {a, b, c}, for which,

a**2 + b**2 = c**2

and such that,

a < b < c

For example,

3**2 + 4**2 = 9 + 16 = 25 = 5**2.

Given an input integer N, find all Pythagorean triplets for which a + b + c = N.

For example, with N = 1000, there is exactly one Pythagorean triplet for which a + b + c = 1000: {200, 375, 425}.


For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

gem install minitest

If you would like color output, you can require 'minitest/pride' in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

ruby pythagorean_triplet_test.rb

To include color from the command line:

ruby -r minitest/pride pythagorean_triplet_test.rb

Source

Problem 9 at Project Euler http://projecteuler.net/problem=9

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

pythagorean_triplet_test.rb

require 'minitest/autorun'
require_relative 'pythagorean_triplet'

class TripletTest < Minitest::Test
  def test_sum
    assert_equal 12, Triplet.new(3, 4, 5).sum
  end

  def test_product
    skip
    assert_equal 60, Triplet.new(3, 4, 5).product
  end

  def test_pythagorean
    skip
    assert Triplet.new(3, 4, 5).pythagorean?
  end

  def test_not_pythagorean
    skip
    refute Triplet.new(5, 6, 7).pythagorean?
  end

  def test_triplets_upto_10
    skip
    triplets = Triplet.where(max_factor: 10)
    products = triplets.map(&:product).sort
    assert_equal [60, 480], products
  end

  def test_triplets_from_11_upto_20
    skip
    triplets = Triplet.where(min_factor: 11, max_factor: 20)
    products = triplets.map(&:product).sort
    assert_equal [3840], products
  end

  def test_triplets_where_sum_x
    skip
    triplets = Triplet.where(sum: 180, max_factor: 100)
    products = triplets.map(&:product).sort
    assert_equal [118_080, 168_480, 202_500], products
  end

  def test_where_sum_1000
    skip
    triplets = Triplet.where(sum: 1_000, min_factor: 200, max_factor: 425)
    products = triplets.map(&:product)
    assert_equal [31_875_000], products
  end
end
class Triplet
  attr_reader :a
  attr_reader :b
  attr_reader :c

  def self.where(min_factor: 1, max_factor:, sum: nil)
    triplets = []
    (min_factor...max_factor - 2).each do |a|
      (a + 1..max_factor - 1).each do |b|
        c = Math.sqrt(a**2 + b**2).to_i
        triplet = Triplet.new(a, b, c)
        if triplet.pythagorean?
          if sum.nil? || triplet.sum == sum
            triplets << triplet
          end
        end
      end
    end
    triplets
  end

  def initialize(a, b, c)
    @a, @b, @c = a, b, c
  end

  def sum
    a + b + c
  end

  def product
    a * b * c
  end

  def pythagorean?
    a**2 + b**2 == c**2
  end
end

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