binary_search_ruby

binary_search.rb

#!/usr/bin/env ruby 

# Usage: ruby binary_search.rb [debug] 50 0 100
# Returns: [optional: count of tries] @item, when found within first and last (not inlusive)

module Algorithms
  class BinarySearch

    def initialize
      @n = 0
      @debug = ARGV.slice!(0) if ARGV[0] == "debug"
      @item = ARGV[0].to_i
      @first = ARGV[1].to_i
      @last = ARGV[2].to_i
    end
    
    def binarySearch(arr = (@first..@last).to_a, item = @item, first = @first, last = @last)
      if (!last) then last = arr.length end

      if @debug
        puts " try #{@n} "
        @n += 1
      end
      midpoint = (last - first) / 2 + first
    
      if (arr[midpoint] == item) then return midpoint end
      if (arr[midpoint] > item) then return binarySearch(arr, item, first, midpoint) end
      if (arr[midpoint] < item) then return binarySearch(arr, item, midpoint, last) end
    end
  end
end

puts Algorithms::BinarySearch.new.binarySearch