This is part 2 of 2 posts about my experience at the 2019 Asia Sudoku Championship which happened on 25-28th January 2019 in Clark, Pampanga, Philippines. This part will be a breakdown of my thoughts on each round.
Reliving the event by going through the booklets, I feel more positive about the puzzles at the ASC. The grids were very clean and themes for some individual puzzles were stunning. For a competition, I personally enjoy medium to medium-plus difficulty and the hardest grids here I felt were right in that range. There was only one minor mistake in round 4 that may have tripped people up but questionably nothing was done about it.
Round 1: Classics
10 puzzles, 45 minutes
Thankfully the practice from last year’s WSC must have still have had an effect since I was solving at a comfortable pace. My only regret is that I should’ve guessed earlier rather than trying to logically solve the harder grids. Once finished, I looked up to see the clock reading 11 minutes left. I decided to spend 2 minutes checking all the grids and turned in my paper with 9 minutes of bonus points. Sinchai, who was not as careful, saw about 100 points evaporating into thin air since he had a neighbouring duplicate in one of his grids. Ouch.
Points: 245/200 – 5th place
Top score: 305 points by Kota Morinishi
Favourite puzzle: Some nice themes across the board which were appreciated only after the competition. These puzzles were typical of Tetsuya Nishio’s Number Place brand; nice givens and nice solving paths. All of these grids would rank highly in a virtual chart of hand-crafted classic sudokus.
Rounds 2-4 would consist of 3 classics at the start and 2 irregular sudokus near the end. The remaining puzzles were a mixture of mostly basic variants with a few exotic types – totaling to 12 puzzles with a time limit of one hour. I don’t think the sets had any underlying theme.
12 puzzles, 60 minutes
The one hour time limit for just 12 puzzles equates to 5 minutes per puzzle. That’s actually quite generous. I wrote some puzzles for both previous ASCs and remember my contributions being rather difficult. I also read Rohan Rao’s blog on the 2018 ASC (and learnt that hardly anyone finished a round) and initially thought these rounds weren’t finishable. And since the IB wasn’t released in advance; strategizing puzzle selection was impossible.
With this mindset, the panic that came when people started finishing and I was nowhere close was explainable. I had 2 of the highest pointers left (Doppelblock and Greater Than) and made one mistake in one of the Diagonal Sudokus. This was to be my only error in the whole competition.
Points: 191/300 – 13th place
Top score: 360 points by Kota Morinishi
Favourite puzzle: Revisiting the Doppelblock on the flight home, I found it quite pretty.
12 puzzles, 60 minutes
After a quick break it was straight to round three. Seeing a lot of people finishing the last round I was eager to finish this set. Whenever I got stuck for more than a minute or so – I was braver to plug and chug (guessing). This strategy would be employed for the remainder of the competition. I saved about 8 minutes and change, scoring another top-5 finish.
Points: 340/300 – 5th place
Top score: 410 points by Kota Morinishi
Favourite puzzle: The 2nd Clone Sudoku with key-shaped regions. The going back and forth between the two keys was very nice.
12 puzzles, 60 minutes
My regret in this round was not using intuition sooner in the Sunglass Sudoku (at 50 points, it was the highest-valued puzzle in the entire ASC). The Sunglass puzzle type appears in Toketa and I remember solving a lot of them – somehow, here I find myself reluctant to pencil in the most plausible sunglasses without absolute certainty.
Also, it was here that the XV Sudoku had a missing X near the end of the solve, I took 5 seconds to convince myself that the error was not on my part. I did not guess and was quite sure there were no snags that could potentially lead to some mistake-inducing mental lapse in the solving path, therefore I just submitted it as is. Others seem to have notice this minor quibble as well but nothing was done to address this and the round was scored normally. I didn’t manage to save any bonus time here.
Points: 300/300 – 7th place
Top score: 395 points by Kota Morinishi
Favourite puzzle: Sunglass Sudoku was most memorable, but the very clean Thermo Sudoku deserves a mention as well.
Round 5: Tetsuya Nishio Round
10 puzzles, 60 minutes
This was the only round to be given a name and had just 10 puzzles. Was it entirely written by Tetsuya himself?
During the layovers to Philippines me and Sinchai took special interest in the Honeycomb Sudoku. I pointed out that a repeat of the same number pattern all over the 7 main groups of hexagons (for example, having 1-7 running consecutively in each bolded groups) would form a valid solution and that you might be able to pull off a valid 6-number givens puzzle.
Sinchai spent the 2 hour flight pondering this and was convinced that my solution and the one in the IB was the only valid pattern possible given the geometric constraint. He spent the next flight proving this and Eureka! When you rotate the grid in any direction, it emerges that that number pattern just repeats itself!
High five! Demonic laughter!
Our evil plan of referring back to the IB’s answer during the round and substitute whatever the givens were to the number pattern in the IB would essentially turn this puzzle into a simple one-minute dictation exercise.
Now this was puzzle #10, does that mean it would be worth heaps? Did we just hack this round?
The answer to the first question was no – the Honeycomb Sudoku was worth 22 points, the fourth lowest in value. Remember front part 1 that we had access to the new IB at 3am, so we were a tad disappointed it wasn’t worth a million but oh well, free points right?
The answer to the second question came like an ice bucket over the head. Naturally, I start with the Classics and the ones here were tough screws. I had to make a three-layer deep guess early and burnt a lot of clock time. But the thought of having that cushion of free points in puzzle #10 eased my mind somewhat.
After the first page was done, I zoomed to puzzle #10, consulted the IB and forcably try to suppress my smirk while transcribing the digits at a lightning pace.
Muhahahaha…! (record slip).. huh?
It was too good to be true. I ran into a contradiction and had our master theory disproved. I appreciated the comedic turnout of events right then and there, chuckled a bit, gave it one last look, and then moved on to other grids. I had the Honeycomb and Odd-Even View unfinished.
Points: 194/240 – 7th place
Top score: 320 points by Kota Morinishi
Favourite puzzle: Honeycomb Sudoku for the laugh.
The ASC concluded with two nice team rounds. Me and Sinchai were teamed up with two young polite Filipinos: Vicente Chan and a buff Alec Machacon. We were affably dubbed the “Friendship Team” by the organizers. Japan, Korea, China and Philippines had a full team while India competed with their trio. With the right mix of adrenaline and good communication our Friendship Team overpowered the field and won.
Round 6 had 4 Capsule Sudokus where clues from the individual grids feed to a larger Irregular Sudoku. Predictably, we took one each while Sinchai would at intervals crane over other people’s grid to see how the metapuzzle would fit. After shuffling back and forth we finished with about 13 minutes to spare, which was second behind Team India.
The final round consisted of 6 basic variants and teams have to arrange them in an unfolded dice-shape so that neighbouring rows and columns would contain identical digits. We gambled with some educated guesses and saved a lot of time. Once each grid could be individually solved we quickly administer them to whoever felt comfortable with that type. This meant no one was idling and we submitted a few minutes behind Team Japan, another 2nd place finish, which would result in a total time of first place.
I’m not the most gung-ho person about a friendly competition but when we found out during the closing ceremony that our results would not count due to our being multinational – I admit it did left a little pang of disappointment since we were kind of roped in to form the Friendship Team, essentially without consent. (We learnt the team composition just before the rounds were to start and had no idea about later consequences). Sinchai must’ve felt worse since he was seriously contemplating our odds had we were given the choice to compete as a 2-man team. My estimate is that I don’t think we would have won. But second? Plausible.
In retrospect, I understood now why the official winner Indian team were reluctant to compete with the benched Yuki Yamamoto or add one extra Filipino to form a complete team. No sour grapes from me. I had my fun. For our victory, we were given extra medals from the organizer’s seemingly endless supply.
It was lovely to make two new friends and I wish them the best of luck and hope someday we’ll meet again.
Past ASC winners:
2017 ASC: 1st Kota Morinishi, 2nd Seungjae Kwak, 3rd Ma Minglei
2018 ASC: 1st Seungjae Kwak, 2nd Ken Endo, 3rd Rohan Rao