オフラインリアルタイムどう書く#6 参考問題を解いた。 http://nabetani.sakura.ne.jp/hena/ord6lintersection/

intersection.rb

#coding: utf-8
class Intersection
  def to_square(p, q)
    xs = [p[0], q[0]].min.to_i
    xe = [p[0], q[0]].max.to_i
    ys = [p[1], q[1]].min.to_i
    ye = [p[1], q[1]].max.to_i
    pos = Array.new(10, 0)
    line = (xs..xe).inject(0) {|a, i| a + (2**i)}
    (ys..ye).each {|y| pos[y] = line}
    pos
  end

  def union(a, b)
    ary = []
    10.times {|i| ary[i] = a[i] | b[i]}
    ary
  end

  def to_block(str)
    ary = str.split("-")
    a = to_square(ary[0], ary[1])
    b = to_square(ary[0], ary[2])
    union(a, b)
  end

  def count_area(a, b)
    area = 0
    10.times do |i|
      tmp = a[i] & b[i]
      area += tmp.to_s(2).count("1")
    end
    area
  end

  def solve(str)
    ary = str.split(",")
    a = to_block(ary[0])
    b = to_block(ary[1])
    count_area(a, b)
  end
end

intersection_spec.rb

$LOAD_PATH << File.dirname(__FILE__)
require 'rspec'
require 'intersection'

describe Intersection do
  before do
    @intersection = Intersection.new
  end

  describe "#to_square" do
    before :all do
      @exp = [0,0,0,1020,1020,0,0,0,0,0]
    end

    it "四角形の領域を表す配列を返すこと" do
      @intersection.to_square("23","94").should eq @exp
    end

    it "第一引数のが値が大きくても同じ配列を返すこと" do
      @intersection.to_square("94","23").should eq @exp
    end

    it "それぞれの引数のx値を入れ替えても同じ配列を返すこと" do
      @intersection.to_square("93","24").should eq @exp
    end

    it "それぞれの引数のy値を入れ替えても同じ配列を返すこと" do
      @intersection.to_square("24","93").should eq @exp
    end
  end

  describe "#union" do
    it "2つの領域を重ねた配列を返すこと" do
      a = [0,0,0,1020,1020,0,0,0,0,0]
      b = [0,0,0,4,4,4,4,4,4,0]
      @intersection.union(a,b).should eq [0,0,0,1020,1020,4,4,4,4,0]
    end
  end

  describe "#to_block" do
    it "L字領域を表す配列を返すこと" do
      @intersection.to_block("23-94-28").should eq [0,0,0,1020,1020,4,4,4,4,0]
    end
  end

  describe "#count_area" do
    it "2つの領域の重なり合っているマス数を返すこと" do
      a = [0,0,0,1020,1020,4,4,4,4,0]
      b = [0,480,480,480,480,480,511,511,511,511]
      @intersection.count_area(a, b).should eq 11
    end
  end

  describe "#solve" do
    it "サンプルデータ#1の入力に対して正しい値を返すこと" do
      input = "23-94-28,89-06-51"
      @intersection.solve(input).should eq 11
    end
  end
end