WSC/WPC Impressions – October 14 (WSC Day 1)

I really should finish up writing the rest of my impressions series, before I forget about them:

The competition was 2 days of World Sudoku Championship, followed by 3 days of World Puzzle Championship. I qualified for the WPC’s A-team via the US Puzzle Championship, and tagged along as a B-team member of the WSC simply because there was still room for me to join. As such, I did not expect to perform well on the WSC.

Round 1 was easy classics, which the first puzzle was a 4×4 sudoku with the numbers 2013. This was followed by three 6×6’s, and then a bunch of easy~moderate classic sudoku. The round was short (30 minutes), and I finished about half of the easier puzzles.

Round 2 was the “common variant” round, where we get to see some of the common (and less common) sudoku variants. This round is significantly longer than the previous, and contains many harder puzzles. The ring sudoku was as I suspected, and could be decomposed into two 5×5 latin squares. I botched the interconnected sudoku on this round, and had to re-solve, wasting a large amount of time. In the end, I didn’t do too well on this round, partly due to the amount of time wasted on the interconnected sudoku.

Round 3 was interesting. The round had 3 envelopes, worth a different amount of points, each containing a set of sudoku jigsaw pieces which you will need to fit on the main board. Opening the A only gives you 100, opening B gives you 50 (regardless of whether you opened A), and opening C gives you only 20 (regardless of whether you opened A or B). I started off with the A, and realized I can’t solve that in a minute, then opened the B. At 7 minutes remaining, I realized I can’t solve that neither, so I opened C. The pieces in C has all the digits filled, so all you need to do is to find how it fits, and copy the digits onto the solution grid. I managed to do that in time, but sadly copying the digits wrong, so in the end I got 0 for this round.

After that was lunch, where they still didn’t have water or tea. Round 4 was more classics, except this time they were much harder than the ones in Round 1. I ended up solving only 2 out of 8 on this round, giving me a disappointing score of 46 out of 230. I probably should have guessed on some of them.

Round 5 consisted of variants that had to deal with arithmetic, such as sum, arrow, product, and killer. When I looked at the product, I laughed as I have never seen the products being stacked like that before. I wasted a lot of time on the sum sudoku in this round, which did not came to fruition.

Round 6, 7, and 8 were the team rounds, where we have a group of 4 players solving a set of puzzles together. From my experiences from previous WPC, these can often be brutal, especially to weaker teams. Round 6 consists of six 9×9 sudokus and twelve 4×4’s, which we need to solve and then clue together to form a ball in such a way that the digits of the glued sudokus match. As we suspected, we can’t solve any of the large sudokus alone, but have to refer to the small ones to find what is and what isn’t possible. This meant that we had to go through a tedious checking process to see what corner can be fitted with which sudoku. In the end, we were only able to place together 3 corners on a single sudoku, and that still wasn’t enough to solve it, which gave us a big fat zero.

Round 7 was the matchmaker, where you are given 8 different variants and were told that they could be matched in pairs so that each pair has the same solution. A practice for can be found on the Logic Masters India website: The first 2 pairs were relatively easy to find out, which we gave to Carolyn and Anil to solve. However, we were unable to determine how the last 4 sudokus paired up, and in the end only Carolyn’s pair was solved. On the plus side, this meant that we didn’t get zero on this round.

Round 8 was the Mahjong round, where we were place the given Mahjong tiles onto the grid subjected to sudoku rules, as well as additional rules given by lines drawn on the grid. During the solve, we ended up guessing a large chunk of tiles, as we could not logically determine the direction of one of the line give by the additional rules. Luckily this was correct, and we had 48 tiles placed.

This concluded day 1 of the WSC, which was followed by dinner and bed. *and Sudoku GP* While I wasn’t particularly pleased with my experience, it was within my expectations given that I had no training coming into the WSC. Next year, I will do better.

Edit: What was I thinking. The Sudoku Grand Prix was on the 1st day of the WSC, not the 2nd day. The GP was a series of 8 online sudoku contests organized by the World Puzzle Federation, where each of them is ran by a different countries. The top 10 contestants of the GP were invited to the finals, which was hosted on the night of the 1st day of the WSC. Unlike the WSC and WPC, the play-off is a very simple structure. The first person to solve all 8 puzzles (one from each host) is declared the winner. It was very nice to have the set of puzzle available for the spectators, so we don’t have to simply sit there while the competition was going on. Furthermore, we have commentary from our own Byron Calver and UK’s Tom Collyer. The commentary were both witty and informative, giving us background on the various puzzle authors, as well as numerous tennis jokes on the tennis sudoku. The GP was eventually won by Kota Morinishi, one of the best Japanese solvers and (as we shall see) the 2nd place winner of WSC this year.


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