Friday puzzle 2 -- Trains

question

Does it matter where the engine ends up?

Six

Not that easy :-(

Did you perhaps leave A on the siding at the bottom rather than where B started out?

That's what I did when I thought I had it in six.

If not, please post your six-step solution.

Yes

I was wrong, the engine does have to return to its original spot.

Dan, can you use your moderator powers to delete my "no" response?

Re: Yes

Done ;-)

Seventeen

Now Sixteen

Would you believe seven...

Yep, I left it on teh siding not at B to get to B you need seven moves.

Lee

Re: Would you believe seven...

I don't see how. I can do it in nine steps not returning the engine to its original position, which I inadvertently left out of the original statement (see Dan's question).

Bill's got the count matching the best way I have seen so far.

:-)

Re: Would you believe seven...

I can see seven moves, leaving one car in a siding and returning the engine to the original position.

I can also see seven moves to swap the car positions, but not return the engine to the original position.

Re: Would you believe seven...

I can see seven moves, leaving one car in a siding and returning the engine to the original position.

Yes, or six without returning the engine to its original position.

I can also see seven moves to swap the car positions, but not return the engine to the original position.

Okay, I'll have to think about that. I can't get any better than nine.

Time for Solutions?

Bill, you want to do the honors with your 16-operation solution?

Lee, I agree with Bill on seven step solutions either not returning the engine to its original position or leaving one car on the siding. Is yours something else?

Here's a solution without returning engine to original position:

1) Engine to right, hook up with A

2) Engine and A to bottom

3) Engine and A to bottom siding, unhook A

4) Engine to right, hook up with B

5) Engine and B to top, unhook B (at original site of A)

6) Engine through tunnel to A, hook up

7) Engine and A to right, unhook A (at original site of B)

sixteen step solution

1) engine moves from upper siding to upper track & couples to A

2) engine & A reverse through both switches to lower track

3) engine pushes A onto lower siding & uncouples from A

4) engine exits lower siding to lower track

5) engine reverses direction through diverging switch and circles around upper track, through the tunnel to couple with B on the lower track

6) engine pushes B onto lower siding & couples A to B

7) engine pulls B & A from lower siding onto lower track.

8) engine reverses direction, pushes A & B through diverging switch onto ascending track and uncouples A from B

9) engine pulls B back onto the lower track.

10) engine pushes B into lower siding and uncouples from B

11) engine proceeds to lower track, through tunnel and all the way around to couple with A

12) engine pushes A to lower track and uncouples from A

13) engine proceeds to lower siding and couples with B

14) engine pulls B onto lower track

15) engine pushes B through diverging switch to the upper track and uncouples from B

16) engine returns to upper siding

:-)

Very good! Interestingly, you don't even need the bottom siding, although it takes two more steps without it. (By the time you have worked out the sixteen-step solution you gave, the eighteen-step version without the bottom siding is pretty natural.)