reverse_on_diagonals.rb

def reverseOnDiagonals(matrix)
    array = Array.new(matrix.length){Array.new matrix[0].length}
    x = matrix.length - 1
    y = matrix[0].length - 1
    a = 0
    b = 0

    # reverse the first longest diagonal

    while (x >= 0)
          array[a][b] = matrix[x][y]
          x = x - 1
          y = y - 1
          a = a + 1
          b = b + 1
    end

    # reverse the second longest diagonal

    x = matrix.length - 1
    y = 0
    a = 0
    b = matrix[0].length - 1

    while (x >= 0)
          array[a][b] = matrix[x][y]
          x = x - 1
          y = y + 1
          a = a + 1
          b = b - 1
    end

    # fill in the rest

    x = 0
    y = 0

    while (x < matrix.length)
        while (y < matrix[0].length)
              if array[x][y] == nil then
                 array[x][y] = matrix[x][y]
              end

              y = y + 1
        end

        x = x + 1
        y = 0
    end

    return array
end