二分探索(出来損ない)

binsearch.rb

def bnsearch (*array,&block)
  low = 0
  up = array.length - 1
  while(low <= up)
    mid = (low + up) / 2
    if (array[mid] <=> block.(array[mid])) == 0
      return array[mid]
    else if (array[mid] <=> block(array[mid])) == -1
      low = mid + 1
    else
      up = mid - 1
    end
  end

  return nil
end

bnsearch([*1..10]){|x| x == 5}