Minesweepers Mapping (December 2025 Challenge Question)

Sectors A1 and I9 both get two sweeps… I can’t quite see how this could be avoided.

I think this is a correct solution, so a GA.

Each soldier does not need to sweep either: his starting or finishing square.

So they will possibly blow themselves up before getting going? If each sweeps their 1st square, it doesn’t violate any conditions?

Exit at H9 or B1, respectively?

Orders do not state ‘exit’ the area, ordered to begin and end the exercise at specified points within the area.

Yes, but then you sweep two zones twice, or don’t sweep the zone you start in, a paradox within the challenge question….

Agreed, this is my point exactly in #7.

So… there is a different solution that (apparently) none of us has discovered where all directive of all orders are not in conflict, thus the solution Randall has offered is incorrect.

OR… one of us groundpounders gets to advise the sergeant that the order should be reviewed and restated or clarified.

My general inclination of adapt and overcome says, sweep the sector of my assigned start point, sweep the sectors along the travel route plotted by Randall, end the exercise at my assigned destination without sweeping the sector of my destination point.

That seems to work, good show!

That seems to work, good show!

I agree. Soldier 1 sweeps point B and Soldier 2 sweeps point A. They do not sweep their own start point and they sweep the others start point

If they don’t sweep their start point, they may never complete the mission? Better to not sweep their exit point, knowing it has been swept by the counterpart. However, this should have been addressed in the original conditions, as it appears to violate the conditions given.

GA

I've been waiting for about 5 hours for chat gpt to tidy up that image. It should be clear enough.

It would be really impressive if CHAT GPT could solve the puzzle...

FIGURE 1

I solved this for 3x3, 5x5, and 7x7 and noticed a pattern for this puzzle, 9x9. There is a symmetry where soldier 1 starts at the top left corner and soldier 2 at the bottom right. So if you know the paths for soldier 1 you know the paths for soldier 2, symmetrically opposite pivoted on the lake.

Here is the pattern shown as a matrix of sectors with the number indicating which soldier swept each as 1 or 2 or X for the lake.

3x3:

1 2 2

1 X 2

1 1 2

5x5

1 2 2 2 2

1 1 2 2 2

1 1 X 2 2

1 1 1 2 2

1 1 1 1 2

7x7

1 2 2 2 2 2 2

1 1 1 2 2 2 2

1 1 1 2 2 2 2

1 1 1 X 1 1 1

1 1 1 1 1 2 2

1 1 1 1 1 2 2

1 1 1 1 1 1 2

9x9

1 2 2 2 2 2 2 2 2

1 1 1 1 2 2 2 2 2

1 1 1 1 2 2 2 2 2

1 1 1 1 X 2 2 2 2

1 1 1 1 1 2 2 2 2

1 1 1 1 1 2 2 2 2

1 1 1 1 1 2 2 2 2

1 1 1 1 1 1 1 1 2

path through 9x9, soldier 1 (see FIG 1 above)

1A 2B 2C 2D 3D 3C 3B 3A 4A 4B 4C 4D 5D 5C 5B 5A 6A 6B 6C 6D 6E 7E 7D 7C 7B 7A 8A 9A 9B 8B 8C 9C 9D 8D 8E 9E 9F 9G 9H ending at 9I

soldier 2 path is symmetrical about center square 5E (the lake).

1A to 2B appears to be diagonal?

1A to 2B appears to be diagonal?

Thanks, should be:

1A 2A 2B 2C 2D 3D 3C 3B 3A 4A 4B 4C 4D 5D 5C 5B 5A 6A 6B 6C 6D 6E 7E 7D 7C 7B 7A 8A 9A 9B 8B 8C 9C 9D 8D 8E 9E 9F 9G 9H ending at 9I

Where should a diagonal step take place ? 1 A steps forward into 2A then executes a left turn into B2 ! Going diagonally from A1 to B2 means the soldier misses A2.
Point 4 of the instructions clearly state no soldier is allowed to move diagonally !

He did have a diagonal in his original sequence, this fixed it.

If they start at Point A or B, and exit at Point A or B, then they sweep those areas twice, or do not sweep them at all, violating one or another condition.

Is easy to figure out and display in a Excel Table converted into a Powerpoint JPEG Foto.

And now, to further muddy the water a bit: The actual question is

”What is the optimal path?”

Optimal… by what measure? The maps in posts #14 and #18 there are 21 right angle turns on the path. The map in #1 has 25 right angle turns on the path. Does this make #1 less optimal than the others?

Arrrgh! Only a week ago I started a thread about paralysis by analysis!

(Somebody check my counts, would ya?)

There is more than 1 way to do the job - I just hope Sad Sack is not my partner.

I started A doing column A 2 to 9

then do column B 9 to 5

then row 5 C and D

then walk like a bumble bee and do columns C and D to C 9

then Row 9 D and E

then up and down columns E to H rows 6 to 9

and finally when you reach H9 step into I9 and ask B's wife to sweep the block if she is not blown to pieces already.