# paulfioravanti's solution

## to Queen Attack in the Ruby Track

Published at Jul 13 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

In the game of chess, a queen can attack pieces which are on the same row, column, or diagonal.

A chessboard can be represented by an 8 by 8 array.

So if you're told the white queen is at (2, 3) and the black queen at (5, 6), then you'd know you've got a set-up like so:

``````_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ W _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ B _
_ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _
``````

You'd also be able to answer whether the queens can attack each other. In this case, that answer would be yes, they can, because both pieces share a diagonal.

For installation and learning resources, refer to the exercism help 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 queen_attack_test.rb
``````

To include color from the command line:

``````ruby -r minitest/pride queen_attack_test.rb
``````

## Source

J Dalbey's Programming Practice problems http://users.csc.calpoly.edu/~jdalbey/103/Projects/ProgrammingPractice.html

## Submitting Incomplete Solutions

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

### queen_attack_test.rb

``````require 'minitest/autorun'
require_relative 'queen_attack'

# Common test data version: 2.0.0 44a1e12
class QueenAttackTest < Minitest::Test
def test_queen_with_a_valid_position
# skip
assert Queens.new(white: [2, 2])
end

def test_queen_must_have_positive_row
skip
assert_raises ArgumentError do
Queens.new(white: [-2, 2])
end
end

def test_queen_must_have_row_on_board
skip
assert_raises ArgumentError do
Queens.new(white: [8, 4])
end
end

def test_queen_must_have_positive_column
skip
assert_raises ArgumentError do
Queens.new(white: [2, -2])
end
end

def test_queen_must_have_column_on_board
skip
assert_raises ArgumentError do
Queens.new(white: [4, 8])
end
end

def test_can_not_attack
skip
queens = Queens.new(white: [2, 4], black: [6, 6])
refute queens.attack?
end

def test_can_attack_on_same_row
skip
queens = Queens.new(white: [2, 4], black: [2, 6])
assert queens.attack?
end

def test_can_attack_on_same_column
skip
queens = Queens.new(white: [4, 5], black: [2, 5])
assert queens.attack?
end

def test_can_attack_on_first_diagonal
skip
queens = Queens.new(white: [2, 2], black: [0, 4])
assert queens.attack?
end

def test_can_attack_on_second_diagonal
skip
queens = Queens.new(white: [2, 2], black: [3, 1])
assert queens.attack?
end

def test_can_attack_on_third_diagonal
skip
queens = Queens.new(white: [2, 2], black: [1, 1])
assert queens.attack?
end

def test_can_attack_on_fourth_diagonal
skip
queens = Queens.new(white: [2, 2], black: [5, 5])
assert queens.attack?
end

# Problems in exercism evolve over time, as we find better ways to ask
# questions.
# The version number refers to the version of the problem you solved,
#
# Define a constant named VERSION inside of the top level BookKeeping
# module, which may be placed near the end of your file.
#
# In your file, it will look like this:
#
# module BookKeeping
#   VERSION = 1 # Where the version number matches the one in the test.
# end
#
# http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html

def test_bookkeeping
skip
assert_equal 2, BookKeeping::VERSION
end
end``````
``````class Queens
BOARD_BOUNDARIES = (0..7)
private_constant :BOARD_BOUNDARIES

def initialize(options)
@positions = options.values
raise ArgumentError unless valid_positions?
end

def attack?
same_row_or_column? || same_diagonal?
end

private

def valid_positions?
positions.flatten.all? { |value| BOARD_BOUNDARIES.cover?(value) }
end

def same_row_or_column?
positions.transpose.any? { |pos1, pos2| pos1 == pos2 }
end

def same_diagonal?
positions.transpose.map { |pos1, pos2| (pos1 - pos2).abs }.uniq.one?
end
end

module BookKeeping
VERSION = 2
end``````