Spiral Printer

gistfile1.rb

class NotSupportedArraySize < StandardError; end
class SpiralPrinter
  def print(array)
    finalResult = []

    size = array.length
    modulo = Math.sqrt(size).to_i

    raise NotSupportedArraySize if modulo**2 != size

    peelingIndex = 0
    startIndex = 0
    endIndex = size
    method = :upto
    leftOvers = []
    onTrack = array.dup

    return "#{array[0]}" if size == 1

    while onTrack.length != 4 do
      sqrt = modulo if sqrt.nil?
      if peelingIndex > 0
        startIndex = onTrack.length-1
        endIndex = 0
        method = :downto
        sqrt = Math.sqrt(onTrack.length).to_i
      end

      realIndex = 0
      for i in startIndex.send(method, endIndex) do
        if realIndex < sqrt
          finalResult << onTrack[i]
        elsif (realIndex+1) % sqrt == 0
          finalResult << onTrack[i]
        else
          leftOvers << onTrack[i]
        end
        realIndex += 1
      end

      onTrack = leftOvers.compact
      leftOvers = []
      peelingIndex += 1
    end

    onTrack = onTrack.reverse if peelingIndex > 0

    onTrack.each_with_index do |item, index|
      if index == 2
        finalResult << onTrack[index+1]
      elsif index == 3
        finalResult << onTrack[index-1]
      else
        finalResult << item
      end

    end

      finalResult.join(",")
  end
end

describe SpiralPrinter do

  it "should be able to print a spiral of an array of size 1" do
    subject.print([1]).should == "1"
  end

  it "should be able to print a spiral of an array of size 4" do
    subject.print([1,2,4,3]).should == "1,2,3,4"
  end

  ### |1,2,3|      |1,2,3|
  ### |8,9,4|  =>  |4,5,6|
  ### |7,6,5|      |7,8,9|
  it "should be able to print a spiral of an array of size 9" do
    subject.print([1,2,3,8,9,4,7,6,5]).should == "1,2,3,4,5,6,7,8,9"
  end

  ### |01,02,03,04|      |01,02,03,04|
  ### |12,13,14,05|  =>  |05,06,07,08|
  ### |11,16,15,06|      |09,10,11,12|
  ### |10,09,08,07|      |13,14,15,16|
  it "should be able to print a spiral of an array of size 16" do
    subject.print([1,2,3,4,12,13,14,5,11,16,15,6,10,9,8,7]).should == "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16"
  end

  ### |01,02,03,04,05|      |01,02,03,04,05|
  ### |16,17,18,19,06|  =>  |06,07,08,09,10|
  ### |15,24,25,20,07|      |11,12,13,14,15|
  ### |14,23,22,21,08|      |16,17,18,19,20|
  ### |13,12,11,10,09|      |21,22,23,24,25|
  it "should be able to print a spiral of an array of size 25" do
    subject.print([1,2,3,4,5,16,17,18,19,6,15,24,25,20,7,14,23,22,21,8,13,12,11,10,9]).should == "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25"
  end

  ### |01,02,03,04,05,06|      |01,02,03,04,05,06|
  ### |20,21,22,23,24,07|  =>  |07,08,09,10,11,12|
  ### |19,32,33,34,25,08|      |13,14,15,16,17,18|
  ### |18,31,36,35,26,09|      |19,20,21,22,23,24|
  ### |17,30,29,28,27,10|      |25,26,27,28,29,30|
  ### |16,15,14,13,12,11|      |31,32,33,34,35,36|
  it "should be able to print a spiral of an array of size 36" do
    subject.print([1,2,3,4,5,6,20,21,22,23,24,7,19,32,33,34,25,8,18,31,36,35,26,9,17,30,29,28,27,10,16,15,14,13,12,11]).should == "1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36"
  end

  it "should fail if size of array isn't N^2" do
    expect { subject.print([1,2,3]) }.to raise_error { NotSupportedArraySize }
  end
end