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asiviero's solution

to Diamond in the Ruby Track

Published at Jun 09 2020 · 0 comments
Instructions
Test suite
Solution

The diamond kata takes as its input a letter, and outputs it in a diamond shape. Given a letter, it prints a diamond starting with 'A', with the supplied letter at the widest point.

Requirements

  • The first row contains one 'A'.
  • The last row contains one 'A'.
  • All rows, except the first and last, have exactly two identical letters.
  • All rows have as many trailing spaces as leading spaces. (This might be 0).
  • The diamond is horizontally symmetric.
  • The diamond is vertically symmetric.
  • The diamond has a square shape (width equals height).
  • The letters form a diamond shape.
  • The top half has the letters in ascending order.
  • The bottom half has the letters in descending order.
  • The four corners (containing the spaces) are triangles.

Examples

In the following examples, spaces are indicated by characters.

Diamond for letter 'A':

A

Diamond for letter 'C':

路路A路路
路B路B路
C路路路C
路B路B路
路路A路路

Diamond for letter 'E':

路路路路A路路路路
路路路B路B路路路
路路C路路路C路路
路D路路路路路D路
E路路路路路路路E
路D路路路路路D路
路路C路路路C路路
路路路B路B路路路
路路路路A路路路路

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 diamond_test.rb

To include color from the command line:

ruby -r minitest/pride diamond_test.rb

Source

Seb Rose http://claysnow.co.uk/recycling-tests-in-tdd/

Submitting Incomplete Solutions

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

diamond_test.rb

require 'minitest/autorun'
require_relative 'diamond'

class DiamondTest < Minitest::Test
  def test_letter_a
    answer = Diamond.make_diamond('A')
    assert_equal "A\n", answer
  end

  def test_letter_c
    skip
    answer = Diamond.make_diamond('C')
    string = "  A  \n"\
             " B B \n"\
             "C   C\n"\
             " B B \n"\
             "  A  \n"
    assert_equal string, answer
  end

  def test_letter_e
    skip
    answer = Diamond.make_diamond('E')
    string = "    A    \n"\
             "   B B   \n"\
             "  C   C  \n"\
             " D     D \n"\
             "E       E\n"\
             " D     D \n"\
             "  C   C  \n"\
             "   B B   \n"\
             "    A    \n"
    assert_equal string, answer
  end
end
class Diamond
  def self.make_diamond(max_letter)
    rows = Array.new((max_letter.ord - 'A'.ord)*2+1) {[]}

    row_size = (max_letter.ord - 'A'.ord) * 2 + 1
    'A'.upto(max_letter) do |letter|
      letter_diff = letter.ord - 'A'.ord
      rows[letter_diff] = compute_row(letter, row_size)
      rows[rows.length-letter_diff-1] = rows[letter_diff]
    end
    "#{rows.join("\n")}\n"
  end

  def self.compute_row(letter, row_size)
    center = (row_size+1)/2-1
    i = letter.ord - 'A'.ord
    positions = [center+i, center-i]
    row = ' ' * row_size
    row[positions[0]] = row[positions[1]] = letter
    row
  end
end

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