binsearch.rb

def binsearch(ar, v, s=0, e=ar.length)
  #if we have an empty slice, return nil
  return nil if s >= e

  #if we have a slice with one element, return index if it's the value else nil
  return ar[s] == v ? s : nil if e-s == 1

  #get pivot as average of start and end
  pivot = (e+s) / 2

  #search first part if val > pivot, else second
  return ar[pivot] > v ? binsearch(ar, v, s, pivot) : binsearch(ar, v, pivot, e)
end

File.open("tests.txt", "r") do |infile|
  success = 0
  failed = 0
  while (problem = infile.gets)
    ar = []
    v  = Integer(infile.gets)

    infile.gets #skip in [

    line = ""
    while !(line = infile.gets).match(/^\]\?/)
      ar << Integer(line)
    end 

    r = binsearch(ar, v)
    if (line.match(/yes/) and r and ar[r] == v) or (line.match(/no/) and !r)
      success += 1
    else
      failed += 1
      print "#{problem.strip}: fail\n"
    end

    infile.gets #skip empty
  end

  print "Success: #{success} Failed: #{failed}\n"
end