tokyorubyistmeetupのペアプロ課題その1

postal_code.rb

# -*- coding: utf-8 -*-
require "csv"

module PostalCode
  class << self
    def sort
      ary = CSV.read(File.join(File.dirname(__FILE__), "../data/ken_all.csv"))
      sorted = ary.sort_by { |line| line[2] }

      CSV.open("sorted.csv", "wb") do |csv|
        sorted.each do |line|
          csv << line
        end
      end
    end

    def find(postal_code)
      searcher = Searcher.new(postal_code, csv)
      match = searcher.search(0, csv.length - 1)
      match && match[6,3]
    end

    private

    def csv
      @csv ||= CSV.read(File.join(File.dirname(__FILE__), "../data/sorted.csv"))
    end
  end

  class Searcher
    def initialize(postal_code, csv)
      @csv = csv
      @code = postal_code.tr("-", "")
    end

    def search(start_line, end_line)
      half_line = (start_line + end_line) / 2
      row = @csv[half_line]

      if row[2] == @code
        return row
      end

      if half_line <= 0 || half_line >= @csv.length - 1
        return nil
      end

      if row[2] > @code
        search(start_line, half_line - 1)
      else row[2] < @code
        search(half_line + 1, end_line)
      end
    end
  end
end