Suffix Array implementation in Ruby

SuffixArray.rb

# Originally viewed on Giorgio Gonnella's blog
# http://looks-interesting.blogspot.com/2009/07/simple-implementation-of-suffix-array.html
# added substring and binary search 

class SuffixArray

  attr_reader :suf, :string
 
  def initialize(string)
    @string = string
    @suf = (0..string.size-1).sort_by{|i|@string[i..-1]}
  end

  def suffix(idx)
   @string[@suf[idx]..@string.size-1]
  end

  def bsearch(str)
    low = 0
    high = @suf.length-1
    found = nil
    while(low <= high) do
    
      mid = (low + high) / 2
      comp = suffix(mid)
      
      if comp > str
        high = mid - 1
      elsif comp < str
        low = mid + 1
      else
        found = comp
        low = high + 1
      end
      
    end
    
    found
   end 
end