function contains_slow(items, target): # checks every item
   for value in items:

      if value == target:
        return true
   return false             # work grows with length(items)

 function contains_fast(sorted_items, target): # binary search

   low, high = 0, length(sorted_items) - 1
   while low <= high:
      mid = (low + high) // 2
      if sorted_items[mid] == target:
        return true
      if sorted_items[mid] < target:

        low = mid + 1
      else:
        high = mid - 1
   return false             # work grows with log(length(items))
