On Programming: The Answer To The Dave Shields Hacker’s Challenge

In a recent post, On Programming: The Dave Shields Hacker’s Challenge, I posed the following puzzle:

You are driving a cab on a weekday evening in Manhattan. A few minutes past ten you drop off a fare at the southeast corner of Madison and 74th.

Where do you go next?


I know the puzzle is hard.

Usually when I present it, I start by saying that you are approaching Park Avenue and have to decide whether to go uptown or downtown. Most people guess south, saying you want to head downtown to pick up a fare in the midtown area, but the last place you want to be in Manhattan at 10:30 in the evening is near the theater district in Midtown.

A few have guessed north, figuring the obvious answer is south, but none has made it past that point.

I have received no proposed solution in the several days since I posed the puzzle, so here is the solution:

You turn right onto 74th Street, go east for one block. You then make a left turn to head uptown on Park Avenue

The odds are high that you will soon see a domestic servant, who will almost certainly be black, looking for a ride to their home in Harlem.

If you pick them up, the odds are also high that they will appreciate your offering to drive them home, especially since you are white and they are black.

Since they work hard for every penny they make and know that driving a cab is a tough job, the odds are also high that you will get a good tip.

I also posed a followup puzzle:

If your logic is correct and you get the fare you expect, where do you go after you drop them off?


Hint: The cab you are driving is garaged near 57th and 12th.

Here is the solution:

Since your shift ends at midnight, you want to head south towards Midtown, hoping to pick up a short trip on the way.

You know the lights are synchronized on Second Avenue, so you drive down Second Avenue. [1]

However, if the hour is late, and depending on how tired you feel, you may also turn on the Off Duty sign and take your time. If you are hungry you may also stop at the Belmont diner on 28th before heading to the garage on West 57th. [2]

Few jobs provide a better way to meet a true cross section of society than driving a cab. You never know what you will learn when you pick up a fare. Every ride is an adventure.

For example, I once picked up a fare near 54th and 6th. The fare was woman who was carrying a suitcase. She soon started crying. She told me that she had come home to find her husband in bed with another woman. She had thrown some clothes into a suitcase and was taking the cab to her mother’s apartment in Astoria.

I once picked up a fare going from the West Side to Midtown. We went through Central Park, where the traffic was very light. On learning that I was a Caltech graduate, my fare asked me to stop the cab so he could join me in the front seat, where we discussed physics and mathematics for the rest of the trip.

My favorite story from driving in Manhattan was my very first trip. I had left the garage on 57th Street about 4:30 PM on a warm Friday afternoon. I didn’t have the guts to turn off the “Off Duty” sign until I was near Macy’s on 34th Street. As soon as I turned the light off, the door opened and a black woman literally jumped into the cab. She was carrying several large shopping bags and she asked me to drive her to an address in Bed-Stuy. All I then knew about Bed-Stuy was that it was in the far reaches of Brooklyn and that it had one of the highest crime rates in New York City. But a deal is a deal, so I took out my map and eventually delivered her and her packages to her destination.

I expect that trip led to a family legend, for I’m sure that for years afterwards she told the story of how, while waiting for a cab at rush hour in Midtown, she had the good fortune to successfully hail a cab driven by one of the most naive, dumbest, white people she had ever met, and that she was lucky to have reached home without being involved in a traffic accident.

On weekends, when money was not an urgency, I would from time to time leave Manhattan to cruise the outer boroughs, though I did stay away from Bed-Stuy.

My favorite Brooklyn story is that of an elderly black man who asked me to drive him to “Noshenin Avenue.” I dropped the flag and picked up my map. Unable to locate “Nosnenin” I followed his directions. Once we arrived near our destination, I wandered about aimlessly for a few minutes, until I figured out that “Noshenin” was his way of saying “Nostrand.”

Once while driving down Queens Blvd. with two young women in the back seat, I heard one of them say to the other, “So-and-so is such a name dropper. Really. It is too much. After all, I know Francine LeFrak, and I don’t go around all the time bragging about it.” Samuel LeFrak was then a well-known developer. His wealth was exceeded only by his ego, as evidence by the large complex on Queens Blvd. he named LeFrak City.

My most memorable trip as a passenger in the back seat was a run up CPW. The lights on CPW were not synchronized, so the cab came to a screeching halt every few blocks. As soon as the light turned green, the driver floored the pedal to the metal, and we were soon going about sixty miles per hour, passing some cars within inches.

In spite of this, I felt completely safe. When I complimented the driver on his skills, he said he only drove a cab part time. His real job was as a stock car racer, and he had a NASCAR license to prove it.

The education you get from driving a cab is not without cost. To have a job where tipping is an important part makes you appreciate the importance of tips.

Micawber’s Principle applies to driving a cab.[3] To get a dollar when you expect a quarter will make your shift. To get a dollar after driving a fare from JFK to Midtown will ruin your day.

I made less money during my cabdriver days than the increased amount of tips I have since paid out, but I have never regretted tipping handsomely.

The main lesson I took away from my cabdriving days was as simple as it is profound. I found the average New Yorker to be a much better person than most folks would expect. This is true in general, for people are all much the same: richer or poorer, in health or in sickness, happy or sad.

Except for “richer or poorer,” for I found the richer the fare, the scanter the tip, and vice versa.


1. I drove into Manhattan two weeks ago to attend a meeting of the Python User Group that meets in Greenwich Village. Coming from the north, I took the Deegan to the 3rd Ave Bridge and headed down Second. Second Ave. is a good barometer of New York traffic. If things are bad on Second, they are bad everywhere else, so it is as good a route as any. Traffic was bad, but once I got past the 59th Street Bridge the speed picked up, and I also got to enjoy a minitour of the East Village before turning right on Houston.

It was fun to see that Gem Spa, a landmark of the East Village, is still in business forty years after I last partook of one of their great Egg Creams. Sadly, though I knew Ratner’s closed many years ago, I saw no kosher dairy restaurant. East Seventh still houses many Indian restaurants.

I took some pictures and video on my drive down Second, and will post them when time permits.

2. Many people think that parking lots full of taxis or trucks are a good barometer of the quality of a diner’s food. Though the Belmont had good food, cab drivers and truckers are more concerned with finding a parking place than the quality of the food. For example, my daughter Alison, who drove long-haul cross country for several years, met her husband Bruce at a truck stop in the Atlanta area. They live not far from Atlanta today.

3. See Wilkins Micawber:

“Annual income twenty pounds, annual expenditure nineteen pounds nineteen and six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery.”

.The principle is even more memorable if first heard — as I did as a child — spoken by W. C. Fields, in the classic movie The Personal History, Adventures, Experience, & Observation of David Copperfield the Younger

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  1. […] Race and Invisibility In my recent post about a puzzle, I wrote: The odds are high that you will soon see a domestic servant, who will […]

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