def binary_search sortedArr, target
  length = sortedArr.length - 1
  middleIndx = (length / 2).floor
  middle = sortedArr.at(middleIndx)

  if middle != target
    middle
  elsif middle < target
    binary_search sortedArr.slice(0..middle - 1), target
  elsif middle > target
    binary_search sortedArr.slice(middle + 1, length - 1), target
  else
    nil
  end
end