TIMONIUM, Md.—Here’s a math problem for you. Each United Parcel Service Inc. driver makes an average of 120 stops per day. There are 6,689,502,913,449,135,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 alternatives for ordering those stops. Which option is the most efficient, after considering variables such as special delivery times, road regulations, and the existence of private roads that don’t appear on a map?

Even...