I generally don't think it would be fair to use programming in this contest, and in fact I am very pleased with Riad's ideas for optimizer puzzles, which in general are fairly accessible to logical reasoning + taking educated guesses, and wouldn't be trivial at all to do by computer. (Of course the computer software, if you manage to write it, would find the optimal solution. In this year's contest my impression is that optimal solutions to both optimizer puzzles are achievable purely by logical deduction, but we'll only know once my scores on those puzzles become known. In previous year contests the optimizers involved a lot more guesswork for me and I didn't get optimal solutions or see a way to reason entirely logically to find those (even after seeing the optimal solution).

for question 7; voyage:
for example some portion of loop is white cell-10-10-white cell...
answer format should be which: 10 or 10,10 ?
example given does not clarify this.

About programming for optimizer, I agree that it's not the spirit of this test to allow programming. I fail to see how "opti-pentobattle" could be programmed, but "in the citadel" can be modelized by a very classical optimisation problem (I'll probably code it for fun at one point). But despite the tentation, I was happy to notice that for "in the citadel", there was a purely logical way to know if a path is optimal or not (well, until answers are checked, I hope I'm right). I've yet to do opti-pentobattle, so I can't comment on this one.

For now, I'm quite happy to have solved Mirrored Sudoku and Voyage today, afer breaking both of them twice this week-end !

Question for "Borderless Sextet" : that's probably me overthinking, but can the battleships region contain black cells ? I ask only because other types mention it specifically ("possibly with black cells"...) and not battelships. If so, I understand that ships can't go on black cells, so black cells are necessarily water ?

Answer should be just 10. Each block of numbers between white cells gets one number written only.
But if there is a white cell between them, you write one number for every block: e.g. for "white cell-10-10-10-white cell-10-10-white cell..." you will write "10,10".




Yes, the Battleship region can contain black cells. Nothing can be written in any black cell.

Po odnoy. Vsyakiy raz pri vhode linii v zhyoltuyu figuru.

If 10-10-10-white cell-10, the answer should be: 10, 10. The line has twice been recognized as a yellow figure, so 10 twice.
I was originally offered other answer format, but he admitted long. The current format I think difficult to grasp, but this proposal of my Indian friends.

Ships can be only in the blue cells, symbolizing water.

Thank you James for the answers! I did not immediately drew attention to it.

The warning box is still visible in my Opti-pentomino answer. Should I ignore this?

I don't have any error warnings. Do all your rows have 10 characters, even rows that have no pentominos in them?

The pentominos have different set of symbol than what you have submitted (for example J for N). Your submission will be accepted.

Check out my answer to In the Citadel!! This is why I will never be the World Puzzle Champion. Thanks for the puzzles Riad. Never thought I would get so many done.

Haha, I'm hoping you thought it said 'maximise' instead of 'minimise'.

Edited by kiwijam 2016-04-29 3:41 AM

Would someone be willing to spoil the Accordances puzzle?


Edited by rob 2016-04-29 3:24 AM

Check out Cordelia's "wrong" answer for a clue

And thanks James for your sympathy.

So close, I had considered both ingredients.

Sorry David, I hadn't noticed that the rest of your answers and your other optimiser were perfect, and this alone was keeping you from being 1st=. (You know I think you're wonderful.)

Opti-Pentobattle

In the original version of this puzzle it was too easy to find an optimal solution. With the added challenge to minimise the grid size it became a very good optimiser puzzle. Here are my thoughts on the steps needed to solve it.

(On an earlier discussion, I'm not against people using a computer to solve an optimising problem. It is usually very slow to do though. Writing a computer program to solve Opti-Pentobattle is probably a bad idea. There are vast numbers of cases to check, and any insights to speed up the program would also allow you to solve it on paper 10x faster. Although if anyone did successfully write a program I would love to talk to you more about it)

Q1: How many pentominoes are needed?
Two ships always need at least one extra sea cell to join between them.
Three ships would always need two+ extra sea cells.
Ten ships need nine extra cells. So the area must be at least 29 cells, so 6 pentominoes are needed.

Q2: How small can the grid be?
Any 2x2 square can never contain pieces from two different ships.
The fleet contains 7 ships that can fit on one 2x2 square, and 3 ships that fit on two 2x2 squares.
So the whole grid must include at least 13 different 2x2 squares (or pieces of squares).
A 9x5 grid contains 5x3=15 squares, a 7x7 grid contains 4x4=16 squares, anything smaller will not fit the whole fleet.
Of these two, 9x5=45 is better than 7x7=49.

Q3: How can the fleet fit into a 9x5 grid?
At first I could not fit 10 ships into this grid size. But consider this:
Maths: [Imagine the grid has an extra row and column (right and below), it is 6x10.
And imagine each ship has an extra row and column (right and below) of empty space where another ship cannot go.
So a 1-ship "occupies" 4 cells, and a 4-ship occupies 10 cells.
The whole fleet occupies 4x4+3x6+2x8+1x10 = 60 cells, the same size as the 6x10 grid.
So _every_ cell must be used.]
=> Rule for 9x5 grid only: Every 2x2 square that covers some of the 9x5 grid must include a piece of ship. (even overlapping an edge or corner)
Therefore:
- Every corner cell has a ship piece.
- The 4-ship must be horizontal (parallel to the 9-edge) in row 1 or 3 or 5.
There are different ways to do this, e.g. I just created three horizontal rows containing 421, 331, and 2211 ships.

Q4: How do I join the fleet to have a unique solution?
There are some cases you cannot have:
- You cannot join a 1 directly to another 1. Because "1.1" can be swapped with a "3" elsewhere.
- You cannot join two different sizes in a straight line. Because "2.3" might also be "3.2", etc.
- You cannot join a 1 to the end of a 3. Because a V-pentomino containing a 1.3 could also be 3.1.

So this should lead you to a shape that has a unique Battleships solution.
The final step is to find a combination of 6 different pentominoes to cover this shape.
Because only 29 cells are needed for the unique solution, you have one 'spare' cell that can be added anywhere, which should make this step easier.

Also, if you want to solve one of the contestant's 9x5 solutions, use the rules "Every 2x2 square must include a piece of ship" and "Every ship cell cannot diagonally touch another ship cell" will make it much faster.
Most solutions use one of these approaches early on:
- After placing initial pieces there is only one location that the 4-ship can fit.
- After placing initial pieces the four 1-ships have been found, so all other ship pieces are 2+ long.

Edited by kiwijam 2016-04-29 4:41 AM

We have compiled the submissions of Opti-PentoBattle in a pdf. Here is the link. The submissions are not checked for correctness.

All twelve solutions with (Area=45, K=6, N=1) are good.

I seem to have written GOGOGOV instead of GOGOVOV. I think that is my error in the Sextet at least.

I misplaced one Cloud stupidly.

And I had found the 44, but counted it as 42 so didn't submit it.

Not my contest clearly.

Edited by Para 2016-04-29 10:45 AM

my solution to puzzle 1 seems all right to me.
I noticed the same solution has also been submitted by two other players
here is the solution. Is it possible that the puzzle had multiple solutions?

http://web.freepass.it/sf2l/mysoln1.JPG

are the solutions to be posted somewhere soon?
stefano

Edited by forcolin 2016-04-29 1:19 PM

It looks to me that some may have multiple solutions.