WPC 2015

I managed to have time to solve all individual puzzles I could not solve in Sofia. Here is my review of this year.



WSC
I competed officially this year. Normally, in Sudoku contest, I do not think so much about my score, and just solve in the order. But my task in Sofia was acting in place of Hideaki. So I needed to consider my solving order, and concentrate more. Thanks to these efforts, I remember my experience better than last year. I will write about WSC, too.

When I was looking for my seat, I noticed that JPN-A was next to EST-A, and even FRA-A and CZE-A were in the near places. It became a funny area.


Round 1
Left: #10-12
My weakness in Sudoku comes mostly from Classics. Especially, I cannot solve the hardest side well, so just started from easy ones. Safe strategy was enough for me. All puzzles were of reasonable difficulty as a result.


Round 2
Left: Cube, XV, Clone, Diagonal, Classic x2
Another Classic weakness is the lack of speed. This means cheap puzzles can be ineffective, and conversely, if I believe that I would be able to complete high puzzle, it deserves to try. So I started from 1234. It took 12-13mins, but still I feel it was good choice. And it was the enjoyable puzzle in itself.


Round 3
Left: Inner Frame, Max Triplet, Classic #2
This time I feared Max Triplet (and this seems correct), so solved in the order. Cheap Classic is good for the last minutes.


Round 4
Due to wrong deduction, I broke it once, but luckily, I could correct it without erasing so much.

This year, in the one-puzzle rounds, time bonus was reduced. This seems reasonable considering the risk of this structure.


Round 5
Left: Greater-than Consecutive, Kropki, Even Sandwich, Next to 9, Mathrax, Classic x2
Bad result, or I just returned to my usual. Everything was not smooth. Maybe I felt tired after lunch. I like Greater-than Consecutive, and Kropki was instructive for me.


Round 6
Left: Toroidal, Classic x2
Ignored Tridoku at first, and returned to it because the remaining time was not enough for a Classic. Parquet was cool.

I feel "Overlapping Sudoku" is an abuse of the word; it is just a Latin square type without any regional rule. I do not care about the appearance of such types in WSC.


Round 7
In my team, we agreed that ranking in the team is 1. Kota, 2. Takuya, 3. Keisui, and 4. me (same as the order in JNPC this year). And the seats were set as 1->3->2->4.

I solved Extra region quite well. I solved it even faster than Kota. And then I was waiting for Takuya.... He broke it, and needed to restart. I was just sitting for a while, and finally it was relayed. And I broke Irregular! Not enough time for repairing, so I sent it to Kota and he managed to solve the following Classic.

After the round, I learned that the puzzles were actually the same, only numbers were exchanged.


Round 8
In the morning, I heard that I was in the good position for playoff. I had never expected such a chance, and to be honest, it was the first time for me to think about that borderline.

So I decided to start from Twin Region, and solve in the descending order of points. This strategy worked quite well as a result.

In Twin Region, converse sequence was allowed, but it is impossible in fact. This was helpful.


Round 9
I made many errors. Somehow I corrected them all and finished. This was of importance.

I hope gray cells are painted in lighter color.


Round 11
Central part was broken, and Kota repaired it. While repairing, the other 3 were checking, and found that I had made 2 errors inside 6x6. Ah.


And I was in the 8th place. Anyone expected? Kota said that this year there were more puzzlish Suodku. This seems right. I do not mean only newer types were puzzlish. Common types were also on the puzzlish side. This is why I was comfortable, I think.

Also, I made no wrong submission in WSC. I was lucky. I do not expect better results in the future, and even B-team is okay next year. I just want to solve puzzles in WSC.

I am happy with my team result. I felt I achieved my task.


Playoff
Kota: Arrow in 4th - He decided to choose Arrow because of SGP Final.
Tiit: Diagonal in 1st
Jakub: Even Sandwich in 3rd - No problem for Kota, as he agreed later.
Bastien and Seung-Jae: Irregular in 2nd and Killer in 3rd - I forget who chose which.
Michael: Greater-than Consecutive in 1st - It was impressive and I remember it.
Cheran: Extra Region in 2nd
Prasanna and I: Surprise in 3rd - We had same points, surprisingly, and chose the puzzle together. Surprise was attractive, and one more reason for recommending it was to reduce the risk in the final, as a teammate of Kota.
Kota: Inner Frame (remaining) in 2nd
And Surprise was revealed as Non-consecutive.

This was the bonus stage for me, just for amusement. I made fool step in Extra Region (it was Windoku in fact), and while restarting, I was even wondering "why I am here?" Good experience, anyway. Prasanna won the round, so he should have made a good puzzle selection. Later I solved Surprise and it was actually good surprise.

Congratulations on Kota for another title.


At that time, WPC instruction was still not published. I noticed it during sightseeing. If I could have read it beforehand, I had been to the museum.


PGP Final
Killed by the first one again, killed by the word puzzle again. It was too large and tricky for me to grasp. After that I did as usual, but I made a wrong deduction in the Cave and made an error. First error in Sofia. Still, I managed to reach the last puzzle (for the first time in playoff), a bit later than Matus. And Find the Pair benefited me. 3rd place is much better than nothing, like last year.

After the final, I noticed that there were puzzle names on the result table. Were they published before to start? I was always predicting 2 types (except Neighbors).

By the way, after SGP Final, Kota recommended me to prepare a binder because the table mat was uncomfortable. Good advice.


WPC
Like WSC, JPN-A was next to USA-A, and NED-A was near. It was attractive, but Kota chose that seat, so I chose near Ulrich this year.


Round 1
A strange bag was on the table. Puzzles were not normal, as expected. I solved in random order and checked carefully after solving each puzzle. Tapa was 2nd for me, and I left it for the last when I noticed it was not unique. I had more than 20 mins when I returned to Tapa. The problem was, if Tapa was valid, another error means no partial credit. So I checked all puzzles again, and fixed an ambiguous place in Fillomino (in dividing puzzle, dashed line is much better, by the way). That was all.


Round 2
Left: Clouds x2, Triangular Minesweeper (2nd)
I broke Coral once, but I did not notice missing 1 in second solve. I was lucky.

Clouds and Triangular Minesweeper was left for the last, and I did not have enough time. One more minute was enough for 2nd Clouds, though.


Round 3
Left: Chaos(2nd), Encrypted Square x2, Kropki (2nd), 2D Magic
Error: Doppelblock (1st)
The error is because I erased too much while solving 2nd one.

I solved in the order, and after I broke hard Chaos, I moved on to random solving.

I showed my weakness - same as in London. I could not believe Ulrich's finish at first. Long way to reach that level.


Round 4
Left: Worms (2nd), Striped Snake (2nd)
The result seems good, but I was not so comfortable. For example, I broke Cave.... Again!? And Worms (1st) was solved in the last seconds. Just lucky.


Round 5
Solved: Japanese Railways x2, Easy as Tapa (1st), Snake in the Naval Forest
After Japanese Railways, I went to Easy as Tapa, but it did not work at that time. Then I started Snake, broke, erased, and broke again. This was in the must-solve list for me, so I was still thinking about it. And there was the announce. I was forced to restart with that change. After that, I was hurried with my bad performance, and broke Easy as Tripod/ABCD123 twice each. At last I returned to small Tapa. This time it went well.

The puzzles themselves are pretty good. And I know that I should have kept my pace regardless of the error.


Round 6
Great construction. When I got ready to claim, I heard Ulrich's voice. Did not notice Zoltan at that time.


Round 7

Tapa by Kota, Fruit Basket by Ko, Akari by Maho, and Pentomino Areas by me. Ko completed faster, as planned, and he joined in Pentomino because the other 2 said they can solve by their own within the time limit. I did not make much progress at that time (around 10-20%?). A bit later, I started to help Akari for secure. After Tapa and Akari were solved, we started to paint (by the way, some of us broke crayon - I hope better tool). After painting, we gave up Pentomino with the little remaining time, and moved on to checking. Sadly, an error in Akari was looked over - it was too large.

Pentomino was solved around 30-40%? in the end. It caused many wrong deductions. I have tried it again, and I suspect that it has many solutions.


Round 8
Left: Puzzle2 and 6
I skipped Puzzle 1 - I did not notice that letter cells must not be used. And skipped Puzzle 2 without any notice (or just thought "triangle to hexagon?"). Puzzle 3 and 4 went well, and Puzzle 5 also worked well, though I feared that maybe diagonal touch is allowed. Puzzle 6 was hard to figure out. At first, I thought that the arrows indicate multiples of 9. In this sense, 9 was not a good example. Then I returned to Puzzle 1, and understood the rule. One problem was that all blank areas are also used once in the example. And I retried Puzzle 6, noticed that it is not multiple but sum. I tried the 1st one with target number 9 and broke it, then noticed that target number can be changed. But no time to retry.


Round 9
Solved in the order, just left Snake for the last. Tapa was solved by intuition. I made some errors in Snake, but I managed to finish.


Round 10
Left: Scissors x2, Mars and Venus (2nd), Cards (2nd)
Error: Checkerboard (1st), normal error in the final step
At first I skipped 4 types above. Nearest Tetromino was by intuition, it worked strangely well. Checkerboard was the most uncomfortable type for me. I should have done the others. I saw Scissors/Mars and Venus for the first time, and both were interesting.


Round 11
Left: Encrypted Skyscrapers, Tetroscope x2, Puzzle Knight x2, Encrypted Square
Error: Different Neighbors (1st), 2 missing digits
Solved puzzles were almost done in order. I tried Puzzle Knight in the end, expecting some points, but it was in vain.


Round 12
Left: Coriolis, Unequal Star Battle
My order was Yajilin, Rectangles, Pentomino, Domino, Different Neighbors, Magnets, Hula-hoop and Kakuro. Kakuro was completed in the very last seconds. If I did not break Domino, maybe I could have solved one more, but it seemed impossible to finish.

Every time I see "hard" Yajilin, it just requires some deep assumption. A bit boring. I used the same tactics in Different Neighbors and Magnets during the competition.


Round 13
I was the faster in my team, though not smooth, and helped Kota because he had broken his puzzle and restarted. Before we completed it, the other 2 finished theirs and began the final puzzle. Later we joined in it, and we alternately checked the small ones. I also checked one, but I feel I should have concentrated on the large one. I contributed little on it. It broke in the last steps, and we could not repair. About 5 pieces were swapped, as a result.


Round 14
Minesweeper and Tents by Maho, Arrows and Snake by Ko, Sudoku and Kakuro by (of course) Kota, and Different Neighbors and Slitherlink by me.

All clues in Slitherlink were revealed soon, and I solved it at first (in fact, it was wrong, and later I was asked to repair it - how stupid I was to make mistake in such an easy puzzle!). Next, I finished Different Neighbors without a clue, and helped Tents and Mineseeper. Both had enough clues then. The main problem was that we broke Arrows, and it affected on other puzzles. At that time, puzzle distribution was, Arrows by Ko, Sudoku by Kota, Kakuro by me and Snake by Maho. I had little progress until some clues were filled. And even after all clues were revealed, it did not work. Only Kakuro was remaining. It was because of a wrong clue which was filled in during previous wrong deductions. I could not find it. From the puzzle design, it was hard to make notes, hard to find errors. It was preferable to use light gray in clue cells, not black as usual.


Playoff
Palmer was in 3rd place, so I decided not to choose Tapa, for example, because he would choose that type. Playoff structure in these two years is good in that it assures certain ranking even if falling down, like me in London. But I think puzzle choice can be affected by the set of members in that round, which may reduce the advantage of preliminary rounds.

When I was sitting alone, Bram and Zoltan came and I heard that puzzle list had published:
2D Magic
Cave
Chaos
Coral Maximum
Different Neighbors
Dotted Snake
Fuzuli
Hexaislands
Kakuro
Kropki
Magic Summer
Pent It Black
Polygraph
Rollercoaster
Surprise Puzzle

Bram predicted that the number of puzzles would be 3/5/7, like in London. That sounds right, and then finalists would choose 3/2/2 each. I had no reason to choose Latin types. I hated Cave because I had broken that type twice in Sofia. I also avoided Polygraph because I felt it has similar aspects with Cave. And Surprise seemed a passive choice. I wanted to solve Coral, but I thought that Palmer would choose it if he can select 2 types. Thus, my first choice was Pent It Black at that time.

At the beginning of the selection, we were told that the number of puzzles were 3/4/5 in each round. It seemed that I can still choose 2, but only 1 for Palmer.

Ulrich: Kakuro in 4th - It seemed reasonable.
Me: Coral in 5th - I feared Palmer would not choose it. He told that it was actually his first choice. I felt I made a bad decision, and...
Palmer: 2D Magic in 1st - What?! I had not expected that choice, and my previous selection got worse. Also, I had not looked at this type in the preliminary round.
Kota: Rollercoaster in 1st - Quite reasonable.
Bram: Pent It Black in 3rd
Ko: Hexaislands in 2nd
Zoltan, Yanzhe, Nikola: Polygraph in 1st, Kropki in 2nd, Magic Summer in 3rd - I forget who chose which.
Ulrich: Chaos in 2nd - Again reasonable.
Me: Different Neighbors in 3rd - Because basically I feel comfortable with this type. Risky choice, though.
Kota: Fuzuli in 4th - Easy to predict.

Then I was waiting for my turn. 2nd Round was surprising. The reason why I did not choose Hexaislands was that I thought it would be easy and make little difference. Later I solved it, and it took an hour. I do not think this "type" does not suit playoff, but I believe "that puzzle" was too hard for playoff. I heard that Surprise was instructionless, and I think this "type" would not match playoff. Anyway, I was relaxed looking at the situation.

And the final started. See also the scoreboard by Takuya.

While waiting, I was counting time in mind, and my 2:51 counting was quite accurate.

2D Magic had good theme. 1-9 appeared once each, in order. I just kept in mind not to forget 0. I made many small errors, but every time I corrected them soon.

Next was Chaos. I feared this, but it went smoothly after a breakpoint.

Different Neighbors had good logic, which I had searched for in some puzzles but never worked. I was a bit lucky.

And Kakuro.... At least I have some experience as a Japanese. In Japan, Kakuro is also called as Sum Cross. This represents the difference of publishers, but it also shows the difference of logic. Kakuro in the final was rather Sum Cross, where addition of some rows/columns works effectively. I was lucky again, to solve this quite smoothly. And the air moved when I submitted this. I noticed something happened, probably I overtook Ulrich.

The last one was Coral. At my first glance, I cursed my selection - it seemed no start point. Actually, there was a place to start, but I made an error in the last steps. Worst error in the final. I needed to restart and lost a minute, but it was still enough. When I submitted, the air moved again, but I thought maybe I made a mistake, and even prepared for that case. More than a minute had passed, but there was no return, so I asked Vladimir, my marker, and then I knew I won. I did not look at the scoreboard until then.

Thank you everyone concerned, especially to Yuta and Kota, who invited me to LMI in 2011. My puzzle world was small then, just knew Nikoli. My first contest, Fillomino Filla, was wonderful, and impression at that time was why I could endure no-championship period in 2011-2012. I hope I will be able to return something to this community.

Still, I understand that I just won the playoff. It seems so hard to perform like Ulrich in preliminary rounds. Long way to go, but I will just keep enjoying.

Hitori

Notice: Toketa vol.3 will be published. See here.



Hitori is the puzzle appeared in Nikoli in 1990. Classical Hitori was only searching puzzle; looking for certain starting points, and searching the row/column of unblackened cells. That was all. It is often said that Hitori is not in favor because of unnecessary clue cells, but I think this is not bad when regarded as searching puzzle.
On the contrary, modern Hitori is rather logical. Especially, in harder puzzle, we need to consider global connectivity, and I love Hitori with this logical deepness. Here, the authors tend to try to make searching easier, and unnecessary clues can actually be unnecessary.

Here is a (modern) Hitori, it would be better not to fill in empty cells....

solve in PUZ-PRE


Most Hitori I have solved in contests are classical searching ones, where noise clues are valid. I want to solve logical Hitori more.
By the way, Hitori Round in Logic Masters 2014 was great. It suggests some ways to resolve problems about Hitori.

GP 2015 and the result of JPC

GP 2015 was over. I will talk about the puzzle side as usual.


From my experience, the difficulty of each round was well balanced, its quality is almost surprising. Only Round 8 was on the easy side for me, but looking at overall result, it seems to be no problem.

About puzzles: when I saw the larger grids in the first round, I feared that this series would be a bit monotonous, but it was the character of that round in the end. All round had their character.
Speaking more about some rounds, I felt typing in Round 3 was too much. The theme of Round 7 was not preferable even if it was mentioned. It was not of pure logic, and I think it can have cultural aspects. Creating puzzles with such solutions is a good effort, but I think they should have better places to be shown.

The choice of the puzzle types was also good. Maybe LITS was too much, though. It would be better if the point distribution was more balanced between each type.


I want to say more about non-puzzle thing. Since there were many puzzles, I want to know beforehand how many pages puzzlebooklet is. And PGP included point table, whereas SGP did not. This was inconvenient.

Scrolling answer form was tedious. This was also because of the quantity of puzzles. Basically, I solve in the order, and submit less time, so I could reduce my scrolling time, but I felt it could lead to some errors. Hope some changes, if possible.


Finally, about my performance. I lost many points in the first half from errors, so I checked so carefully in the latter half. It was not comfortable, but of importance. I think I have a good advantage, but I still suspect that this came from high bonus ratio.



The next is about Japanese qualification. My rank was 5th in JNPC and 3rd in JPC, completely as I desired. The problem is that both contests were not well organized. JNPC had 2 image errors, and 61pts/600 was added to all participants. JPC was worse, it was too easy. My final score was 870, which I submitted in 105min/150. Last 30 points were determined by luck. Long way to improve.

Due to JPC ranking, there would be some changes in the seats of GP finals. And I decided to compete in WSC officially. I need to prepare for my toughest week ever.

JZC 2015

After JdZdC 2014, JZC 2015 was held in March. You can see puzzles here.
Maybe Round8 is useful for the 24HPC Japanese Round, isn't it?


This year, I prepared Round4 with Takeya. This round includes Classic Nurikabe and 3 variations.
Rules of variations are,
Overlapping:  each grid should be valid as Nurikabe
Pairs: from MellowMelon
Borderline: numbers on the edge must be placed in one of the two neighboring cells

And about bonus puzzles:
Top left: Classic Nurikabe
Top right: Pairs
Bottoms: as you can see from names and images


My main targets this year were,
To use hard classic logic and
To make intuitive Classic
In fact, both are I tried for a long time.

"Hard logic" is just reuse of what I know well, and some Japanese should be especially familiar with this logic. So the second target was rather harder, and I fully used my knowledge about how this type can be unique. I relied on solver for checking, and thanks to it, I think I obtained some new insights. They should be useless, though!


And I also made a Tapa for exhibition. As an exhibition puzzle, I tried to use some useful steps for competitions.

24HPC in Japan, and a bit about JPC

On May 4-5, some Japanese puzzlers solved puzzles from 15th 24HPC in Joes' home. Almost two months have passed, but these days I have some time to review and solve the remaining puzzles,  so here are some notes about my experience and feeling. Scores can be seen here as a reference (I think you need to download to view properly).



Round 1
Lovely theme. My target that day was 900 points in each round, and I thought both of Magnets variants are low valued compared to the amount of work, thus I started from Japanese Sums and went backwards. After going back, I moved on to Magnets, but I broke it and I did not have enough time to retry.

I felt Compass has more chances to work well with other rules.


Round 2
I started from the highest. 25 minutes were left after smooth solve. My plan was not checking till the end, but taking rest after checking once. I used 5 minutes in this round, and it turned out to be error-free.


Round 3
Started from Four Colour Masyu and then Exclusive Mix, but sadly I made a mistake in the last cells of Masyu.

First one of Skyscrapers [Chaos] was harder than expected. Considering the point value, I feared to solve second one and solved Tents and Trees, which I saved for last, in the end of the round. But that Skyscrapers actually was very comfortable one. I regret having passed it.


Round 5
We solved all 14 rounds, but the Japanese round was the last round because some participants are authors/test solver. So next was Round 5.

This was my second choice for ignoring round,  and in fact I should have chosen this round. Targeting 900, I started from Voyage to France, but this was the start of the collapse. One more trouble was in DNA Sudoku. I thought the letters were only for "easier tracking", and believed the connected point was 5.

Second Tapa was my error. I like Spy Battleships type, by the way.


Round 6
My most disappointed round. Mainly because I broke Summons many times, and because I could not find how to solve Loopki. Changing a puzzle into another type is my favorite, but I even broke it! And I feel Loopkis are great, too. I had checked the patterns, but did not understand it enough.

I regret not solving Compass, too. Yes, I could not find the entrance at first glance, but giving up good puzzle is my sadness.


Round 7
I could not finish second Star Battles, and the others are my errors.

In my feeling, points distribution is inappropriate in many places, and hard puzzles tend to be try&error.


Round 8
75 minutes for solving, 5 minutes for checking, 20 minutes for the rest; same as Round 2. The difference is that I made errors.

The puzzles are stable. I am curious about the unfamiliar grid size.

Slash Pack can be solved so easily when uniqueness are used. It is too much valued in this sense.


Round 9
I wanted to solve at least one Battleships in Hexagon, but they were impossible. I have not solved them yet. Frankly, this type breaks the round. IFF rule should be inappropriate here.

Second Thermometer-Ying Yand had no solution. It was easy to find, so during the round we discussed and decided to treat everyone as correct. Scrabble had multiple solutions (probably 3 patterns were submitted at that time).


Round 10
My ignoring round. Arrow Maze was marked incorrect because of ambiguity, but I felt it is solvable. Even if this was ok, this is still my least raw score, but I made a bad choice in the sense of contest points.

They are much amount of try&error and were a bit too hard. In Arrows, I prefer second one for the same reason.


Round 11
Same experience as Round 2 or 8. Surprisingly, every time when I saw my watch, it showed "1:15". The puzzles were comfortable and good for the rest. It had been better if I had used symmetry in first Triple Block.


Round 12
15 minutes were left. I began feeling tired, and the puzzles themselves were harder than in Round 2. I solved intuitively in Fillominoes.

I started from high pointers again. Consistent theme through two rounds.


Round 13
Wonderful theme! I enjoyed Pentominoes thanks to this theme. And here is my joking error in Scrabble:

In Japanese pronunciation it can be B.... Our typical confusion is L/R, but B/V here.

Another error was in first Mastermind. It is so confusing to use a digit twice.

I felt first Group Sum Doppelblock is easier than second one. I am missing something with this type?


Round 14
Because of some troubles, I had little time for Dissection. I managed to solve two of them in the very last second. Satisfying spurt.

Stable Serkan round as usual.


Round 4
To be honest, this result was not expected. I am still wondering why. It is true that I am familiar with authors and puzzle types, but I think these are not enough to explain. What was critical?

I left 15 minutes for second and third of Honey Islands and Curve Data, and solved these four puzzles one by one. I finished in the last minutes. Considering authors, I do not recommend to solve these types earlier.

Here is a strange error:

Bodyless snake!

Second Battleships has cool logic.


Overall
We hold this event since last year (same days). I remember that last year I thought "I do not want to solve Latin squares, but nothing I can solve is left except these!" again and again. This year I do not hate these anymore, and I could enjoy more thanks to this improvement.

Next year, if puzzles are in public, we would like to use the same holidays again. We have many holidays in the first week of May, and this is called as "Golden Week".




Next, about JPC.

JPF has announced the schedule of JPC and JNPC;
JNPC: July 11 13:00-15:00
JPC:   July 25 13:00-15:30
Both are in JST.

Timings are fixed, but international participants are welcome of course. I expect English instructions from organizers.

Systems of WPC and WSC team selection are:
1. Top 4 players are in A-team.
2. Next 3s are in B-team.
3. If these 7s include at least one newcomer, next one is in B-team. If not, top newcomer is in B-team.
No one is seeded.

JPC is the event I can find least meaning for win. I still remember my disappointment two years ago. Ko is not in organizing team this year, and the selection is tough as usual. At least I have the right to go to Sofia because of Puzzle GP, but.... Let's see what will happen.

Two contests are held in different days this year, so I will join in JNPC, too. My fear is that I accidentally get A-team seat. I think the tendency of JNPC is different from that of WSC or other contests; it is rather puzzlish. With my position and eagerness about Sudoku, it is enough for me to compete unofficially in WSC.


By the way, about "puzzlish Sudoku" in conclusion. I do not think only the combinations with typical puzzle type are puzzlish. I do not have enough words to explain the difference well, but a typical example is Killer Sudoku; Japanese authors tend to make this type without fully using cages, and I am comfortable with this just as a puzzler.

It seems that some sudokers do not want a part of puzzlish Sudoku. But I do not know where is the boundary. I talked with Kota about this, and agreed that the boundary should be determined. I fear that I cannot meet good puzzles due to the ambiguity today. If you say these types do not fit Sudoku tests, they can appear in puzzle tests. Sudoku is a kind of puzzle, anyway.