Tiit Vunk is the world champion in solving sudoku puzzles!

Round 7 - Spoilers The last individual round of the opening day ended with a round consisting of 12 sudokus, half of which were classic. The time limit was 30 minutes. Basically, each variant was paired with a classic. As a result of solving a classic sudoku, it gave a hint as to which rules the variant should be solved with. Each variant had 3 possible rules, only one of which could be used to solve it. In other words, one sudoku gave the necessary clues to solve the other. I was able to solve 5 sets out of 6 sets completely and for the last pair, I got a solved classic sudoku, as a result of which I found out what the rule of the last sudoku was. However, I did not manage to solve the last one. I got the second best result from this round. The best result was given by the Chinese woman sitting next to me, Dai Tantan, who solved the most expensive sudoku that I did not do, but at the same time left a few cheaper sudokus unsolved. Jakub got 65 points less, Kota 35 points less. So at the end of the day, I got closer to Jakub and further away from Kota. Points (Jakub 2916, me 2794, Kota 2628). The rest sank further.

Round 8 - Uroboros (TEAM) In this round, 9 sudokus were connected so that the adjacent sudokus had the same numbers in exactly the same positions. What this number was, we had to figure out. All we knew was that in the sum of all the sudokus, these numbers were in order of magnitude. Time limit 35 minutes. We managed to solve 3 out of 9 sudokus, which gave us 20-29th place in the team ranking, and 14-18th place in the official team ranking. These were quite difficult tasks and this round was probably not the most successful.

Round 9 - Sudoku Pieces (TEAM) In this round there were 5 sudokus, in addition to which some pieces were given, which had to be placed in the sudoku and then solved. These were quite difficult tasks again. The time limit was 20 minutes. We got 12th place in this round (official 7th), which is a pretty decent result. There was not much missing to have completed one more task. In fact, we surpassed both the China-A and Czech-A teams. The fact that China and the Czech Republic were ahead generally consisted in the fact that there was one killer sudoku in that round, which gave half of the points for the entire round. We got it done, they didn't.

Sudoku GP Final On the evening of the first solving day, the World Sudoku Grand Prix Final took place, where the top 10 solvers qualified based on the GP preliminary rounds. Since several people withdrew from the competition, some solvers from the second ten also qualified for the final. There were 8 sudokus in the final - one sudoku from each country hosting the round. A total of 4 classic and 4 variations, 3 of which were math-based sudokus. During the final, no one could pass me and in the end I managed to win quite convincingly. Kota Morinishi and Hideaki Jo from Japan came in second and third.

Round 10 - Guess no more This was a round with 9 classic sudokus, but it was known that one of them had multiple solutions and one of them did not have a solution according to the rules. These had to be found during the solving process. Time limit 30 minutes. I managed to solve the round 3 minutes before the end of the time limit, but it was a bit over rocks and stumps and I was also a bit unlucky, because at the end when there was a 50:50 chance, I chose the one with a double solution and still had to solve the last one. With the second choice, I would have only had to solve one and I could have simply pointed out to the other that it was a sudoku with a double solution. There was definitely a chance to win by 2-4 minutes from there. I can't say if others experienced the same misfortune, but Jakub was 7 minutes faster, Kota 3 minutes faster and I finished 13th in that round. The second day didn't start badly, but it was only one fairly cheap round and there was still a long day ahead.

Round 11 - Sorted This was the longest and most expensive round. The round was 90 minutes long and most of the tasks were with a mountaineer flag. I managed to solve all but one - and I had a lot of trouble with that one. Hindsight is a great thing, but I was definitely able to solve this round before the time limit ran out. However, since one remained unsolved and one still had a mistake, instead of winning the round, I ended up in 5th place. Jakub only beat me by 27 points and Kota lost by 9 points. Jakub solved a section of the tasks with flags and shared first place in the mountaineer category with German Martin Merker, who was apparently only chasing the mountaineer title during the entire competition. At the end of the round, the standings were: (Jakub 4441, me 4192, Kota 4047). Seungjae Kwak had risen to fourth with 3997 points.

Round 12 - Gappy classics In this round, 5 sudokus were given, four of which had holes in them. The sudokus had to be placed on top of each other in a certain order so that some of the numbers were visible through the holes. The order had to be figured out by yourself during the solving process. Time limit 30 minutes. I managed to finish 8 minutes before the end of the time limit, which gave me 3rd place. Jakub and Jan Žverina from the Czech Republic were one minute faster. Kota was 2 minutes slower and got 4th place. So I increased the gap with Kota more than Jakub and me. Seungjae Kwak from Korea was in fourth place.

Round 13 - Old maid (TEAM) There were 25 sudokus in this round, of which 24 were paired and one was single. The paired sudokus had the same solution and only one of them had to be solved to get points for both. Time 45 minutes. We started by finding pairs and when I managed to find the first one, I solved it. Next, I randomly solved a single sudoku (consecutive). By that time, others had already come up with ideas for arranging the pairs and that's how we arrived at a system where others found pairs and I solved them. This system worked very well and in addition to me, others also managed to solve some of them when the pairs had already been determined. The result was 7th place in the team standings (5th place in the official team standings). Only those teams that were finally among the top 4 in the finals advanced. You can be 100% satisfied with this round.

Round 14 - Double-Cross (TEAM) In this round, there were 12 sudokus, which were connected along the edges to form a double cross on the flag and coat of arms of Slovakia. Time limit 25 minutes. This was a difficult sudoku. We managed to solve 4 of them, but there was also a mistake in one. The result was 20-29th place (official 14-18). We probably also chose a slightly wrong starting point for the solution. The difficulty of the sudoku is characterized by the fact that only the Japanese were able to complete it, and the others were still well short of completing it. Without the mistake, we probably could have been more or less satisfied with the result.

Finals The finals were held on the principle that first the 7th-10th place would determine the best, who would advance to the second final. In the second final, the 4th-7th place would determine the winner of the third final. In the third final, the 1st-4th place would determine the winner. The time difference between the first and last in each final was 5 minutes, the rest in between according to the difference in points. There were 8 tasks in each final, 4 of which had to be thrown out. In other words, 4 sudokus had to be solved. First, the best of the preliminary rounds chose one to solve and one to throw out. Then the second, then the third, and then the fourth did exactly the same with the remaining sudokus. The sudokus for the third final were: Classic, Irregular, Little Killer, Increasing, Symmetrical, Star Product, Point to next, Pencilmarks. Anyone who is interested can either google it or look at the competition guide, which is available on the website. My thinking was that I would choose Symmetrical sudoku and throw out Little Killer. If Jakub makes the opposite choice before me, I decided to choose Increasing sudoku and throw out Pencilmarks sudoku. Star product is also quite unpleasant, but I am able to solve it at a completely normal level. The starting times of the final were as follows: I started 2:25 after Jakub, Kota about 1.5 minutes after me and finally Shiyu Chen, who had advanced from the second final, 5 minutes after Jakub. The selection of the final problems was as follows: 1. First of all, Jakub chose Symmetrical sudoku and threw out Irregular sudoku. This was a surprise, because my most preferred sudoku was Symmetrical. I have nothing against Irregular, but I know that it is a rather dangerous sudoku in the finals, where mistakes are easy to make. Throwing out this sudoku was probably caused by the fact that Kota is known to be a very fast solver of this sudoku, he has decided several finals in his favor with this sudoku. After all, Jakub considered Kota a more dangerous opponent than me and decided to eliminate him. 2. My choice was easy. Increasing sudoku on and Little Killer off. It was obvious that Kota didn't like this choice. He most likely wanted to choose Little Killer. The emotion was memorable anyway :) 3. Kota chose Point to Next sudoku and threw out Star Product sudoku. A pretty good turn of events for me. 4. Shiyu said that it didn't matter to him which one he solved and he also didn't seem very confident that he could fight for a podium place. In any case, he threw out the classic one and left in the pencilmark. After all, he thought that even if he didn't make it, let others mess with it. This choice didn't make me happy, but I didn't make a big deal out of it. I've solved it though and I don't feel insecure. It probably doesn't like others that much either, since others didn't choose it either. However, I had to wait over 2 hours for the final, because in addition to the 1st and 2nd finals, there were also finals in the U18 and O50 categories, all of which lasted about half an hour. Finally, the time came and my tactic was not to look to the side or behind me, where there was a large screen with the current score, while solving. So the rest of the story is purely based on what others said. Jakub solved the first sudoku quite quickly and increased the gap with me to about 4 minutes. Kota, on the other hand, was about 3 minutes behind. The fourth one probably didn't pass Kota. It took Jakub about 6 minutes for the second sudoku. But I did it really well and when I finished my task, according to the spectators, Jakub's advantage over me was about 8 seconds. I didn't see it myself, but Jakub did, and it is known that it significantly affected his confidence and he became nervous. Kota is said to have solved it even faster, but not significantly. He didn't become dangerous because he was so far behind. I finished the Point to Next sudoku significantly faster than Jakub. It took me a little over 3.5 minutes, Jakub was clearly behind and Kota was again a little faster, but still a safe distance from me. The Pencilmarks sudoku branched out surprisingly quickly and when I finished the task and finally looked around, I saw that I was the first to finish and both Jakub and Kota were solving the last task. There were still 2 and a half minutes left. I held my breath until the judge confirmed that my solution was correct and that I was the world champion. I couldn't finish the rest of my tasks within the time limit and since Jakub started the last sudoku before Kota, he got 2nd place. The Chinese woman Shiyu was only on the second sudoku, as far as I remember. Kota claimed that she was about ten seconds away from finishing the last one and probably got 2nd place there too.