Battleships (Full Version)

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opnismry -> Battleships (12/1/2012 5:35:05 AM)

So my strategy has been, so far,
- Draw around given (water, other ship parts)

- Locate 4-ship "carrier"

- Look for other interesting situations

I suspect there are a lot of situational steps embedded into 3. I've been solving these puzzles now, slowly, but on this one I'm stuck.
I shaded in the places where apparently a carrier could go, which is mostly why I got stuck.


nzbee -> RE: Battleships (12/1/2012 12:40:36 PM)

A carrier can't go from the bottom of the 5th column up because you already have 1 piece of a ship where the 5th column intersects with the 3rd row.

opnismry -> RE: Battleships (12/1/2012 8:21:54 PM)

Oh, duh, lol. That does still leave 6 possibilities though.

Enrique -> RE: Battleships (12/2/2012 4:07:27 AM)

When I need to place a battleship (4-ship carrier), I look at the columns or rows where it can be placed, and also the columns or rows at the sides; usually, i found out that the battleship is placed where the columns or rows at the sides are not too crowded.
In this puzzle, notice that at the left you have a 3-column, a 4-column and a 1-column, in that order. Notice also that there are a lot ships at the right of the grid (where a battleship can't be placed). So a logic answer would be to place the battleship in the second column at the bottom; after this, the only possible solution for the first column is to place a cruiser (3-ship carrier) at the top. From then, the solution becomes easier.
I hope it helps.


cosmictrombonist -> RE: Battleships (12/2/2012 4:15:03 AM)

Battleship (4-piece) cannot go in the topmost row because there would be water throughout row 2. Similar concept shows that no cruiser (3-piece) can exist in column 1, row 5-8. Not sure where the next logical move is but eliminating possibilities is essential.

Enrique's answer doesn't justify why the battleship cannot be placed in row 8 columns, 2-4 at the minimum. If you do this however, you will have to do many guessing attempts to deduce a fallacy. Also, why couldn't the third row 4 be the battleship? Logical elimination is sometimes hard to find so a see-what-happens approach must be taken. Good luck!

Boodle -> RE: Battleships (12/6/2012 7:17:36 PM)

This was unexpectedly hard for a medium puzzle!

For the battleship you can eliminate the top row as cosmictrombonist says.

You can also eliminate the 3rd row thus:

looking at the 2nd row, one of the 3 spaces has to be occupied.

if it's A2: then B1-3 would be water, so B5-8 would be the battleship, so A1-3 would have to be a cruiser, which is fine.

if it's B2: then A1-3 would be water, A5-8 can't contain a cruiser so A5-8 would have to contain a 2-piece ship meaning B1-3 would have to be a cruiser. which is fine.

if it's C2: then B1-3 would be water, so B5-8 would be the battleship, so A1-3 would have to be a cruiser, which is impossible as row 2 would then have 2 occupied spaces.

So - there's either a cruiser in A1-3 or B1-3, which means row 3 has to be the other cruiser.

So the battleship is either row 8 or column B. hope that helps to be getting on with!


opnismry -> RE: Battleships (12/6/2012 10:36:03 PM)

I mean, I am still ending up with a lot of possibilities.

I enjoy all of the other number logic puzzles because you can analyze a situation using the puzzle's rules and made a definite deduction or a tentative deduction. It really seems battleships departs from this pattern, and is closer to brute force (trying all possible combinations) than the others. Of course, it is sometimes necessary to make an assumption, but that is usually on on hard puzzles. It looks like even "moderately difficult" battleships puzzles require multiple assumptions in general.

Edit: the dark water is immediately concluded and the light water is deduced afterward. Orange is deduced after dark grey, except in the first diagram, where it represents ambiguity.


Boodle -> RE: Battleships (12/6/2012 10:54:08 PM)

C2 cannot be a ship.

If it were a ship, then B1-3 would be water. then B5-8 would be battleship. then A5-8 would be water. then A1-3 would have to be cruiser. then you would have C2 and A2 both occupied by ship, which would be an error as row 2 can only have 1 square occupied.

opnismry -> RE: Battleships (12/6/2012 10:55:57 PM)

I saw that immediately after I posted it and edited it to reflect that observation.

opnismry -> RE: Battleships (12/6/2012 11:22:52 PM)

After the A2 assumption, and some manipulations, I got the solution.


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