From: brabuhr@...
Date: 2009-06-15T01:56:06+09:00
Subject: Re: [QUIZ] Matrix Rotator (#209)

Hope this isn't too early, but I may be offline for a couple of days,
so I'm posting my method now:

> ## Matrix Rotator (#209)
>
> This week's quiz is write ruby method that will rotate a matrix 90
> degrees counter-clockwise (or ð/2 radians).
>
> Ex:
>    0 0 0 0    0 0 0 0
>    0 X 0 0    0 0 X 0
>    X X X 0    0 X X 0
>    0 0 0 0    0 0 X 0

module Matrix
  def self.rotate(o)
    rows, cols = o.size, o[0].size
    Array.new(cols){|i| Array.new(rows){|j| o[j][cols - i - 1]}}
  end
end

3 tests, 5 assertions, 0 failures, 0 errors:
    assert_equal square_rotated, Matrix.rotate(square)
    assert_equal rectangle_rotated, Matrix.rotate(rectangle)
    assert_equal( [[5], [4], [3], [2], [1]], Matrix.rotate([(1..5).to_a]) )
    assert_equal( [[1, 2, 3, 4, 5]], Matrix.rotate((1..5).to_a.map{|n| [n]}) )
    assert_equal(
      [ [1, 2, 3, 4, 5],
        [6, 7, 8, 9, 0] ],
      Matrix.rotate([ [6, 1], [7, 2], [8, 3], [9, 4], [0, 5] ])
    )