二分探索

binary_search.rb

class Array
  def binarysearch(keyword)
    return "Couldn't find the keyword." if self.size < 1
    mid = self.size/2.to_i
    pivot = self[mid]
    puts self[mid]
    binary = Array.new
    if keyword == self[mid]
      return "Found the number."
    end
    if keyword < self[mid]
      (0..mid-1).each do |i|
         binary.push(self[i])
      end
    else
      (mid+1..self.size-1).each do |i|
         binary.push(self[i])
      end
    end
    binary = binary.binarysearch(keyword)
  end
end