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What it Takes to Wear the Sudoku Crown What It Takes to Wear the Sudoku Crown
(about 1 hour later)
On a mid-October Monday, shortly before 9 a.m., 179 elite puzzlers made their way into the ballroom of a Toronto hotel and found their allocated seats for the World Sudoku and Puzzle Championships. Valentin Miakinen of France positioned a plastic, pigeon-shaped hunting decoy at the front of his desk, for luck. Hwangrae Lee, from Korea, polished his pencil sharpener with a tissue. Quiet descended as proctors distributed booklets for Round 1: nine Sudoku puzzles, with a 45-minute time limit. Thomas Snyder, the general manager of the event, announced: “We begin in 5, 4, 3, 2, 1 — go!”On a mid-October Monday, shortly before 9 a.m., 179 elite puzzlers made their way into the ballroom of a Toronto hotel and found their allocated seats for the World Sudoku and Puzzle Championships. Valentin Miakinen of France positioned a plastic, pigeon-shaped hunting decoy at the front of his desk, for luck. Hwangrae Lee, from Korea, polished his pencil sharpener with a tissue. Quiet descended as proctors distributed booklets for Round 1: nine Sudoku puzzles, with a 45-minute time limit. Thomas Snyder, the general manager of the event, announced: “We begin in 5, 4, 3, 2, 1 — go!”
Dr. Snyder likened that moment — when competitors hurriedly flip open their booklets — to both Christmas morning and the start of the SAT, “a mix of joy and panic,” he said. Based in the San Francisco Bay Area, Dr. Snyder is trained as a chemist and works in immunology and genomics. He also founded and runs Grandmaster Puzzles, a puzzle publishing company. He is a three-time world Sudoku champion, and in 2018 he won the title of world puzzle champion, making him the first person to win both honors.Dr. Snyder likened that moment — when competitors hurriedly flip open their booklets — to both Christmas morning and the start of the SAT, “a mix of joy and panic,” he said. Based in the San Francisco Bay Area, Dr. Snyder is trained as a chemist and works in immunology and genomics. He also founded and runs Grandmaster Puzzles, a puzzle publishing company. He is a three-time world Sudoku champion, and in 2018 he won the title of world puzzle champion, making him the first person to win both honors.
The annual championship event comprises two days of Sudoku, followed by three days of other types of pencil-and-paper logic puzzles. Some of the Sudokus were classics: In a 9-by-9 grid, insert a number from 1 to 9 into each cell so that no number repeats in any row, column or bolded 3-by-3 square region. There were also trickier variants, such as “Difference Sudoku,” for which the standard rules apply, but also each number shown in a circle between two adjacent cells indicates the difference of the numbers in those two cells.The annual championship event comprises two days of Sudoku, followed by three days of other types of pencil-and-paper logic puzzles. Some of the Sudokus were classics: In a 9-by-9 grid, insert a number from 1 to 9 into each cell so that no number repeats in any row, column or bolded 3-by-3 square region. There were also trickier variants, such as “Difference Sudoku,” for which the standard rules apply, but also each number shown in a circle between two adjacent cells indicates the difference of the numbers in those two cells.
Although puzzlers qualify for the event on a national level, most attend just for fun and for the community — to revel with people who share in the same nerdy delight. A member of Italy’s team, Laura Tarchetti, sported a hoodie with a confession on the back: “SUDOKU ADDICTED.” Competitors came from 33 participating countries; the youngest was Toni Borozan, 14, of Croatia; the eldest was Jouni Sarkijarvi, 75, of Finland.Although puzzlers qualify for the event on a national level, most attend just for fun and for the community — to revel with people who share in the same nerdy delight. A member of Italy’s team, Laura Tarchetti, sported a hoodie with a confession on the back: “SUDOKU ADDICTED.” Competitors came from 33 participating countries; the youngest was Toni Borozan, 14, of Croatia; the eldest was Jouni Sarkijarvi, 75, of Finland.
The top solvers are also there to win. (The glory comes with a trophy, but no prize money.) For the Sudoku event, the leading contenders this year included Tantan Dai, 23, who grew up in Beijing and is pursuing a Ph.D. in mathematics at the Georgia Institute of Technology; and Tiit Vunk, 40, a transport engineer from Elva, Estonia, whose wife, Regina, and daughters — Elis, 16, and Iiris, 11 — joined him on the trip.
Ms. Dai and Mr. Vunk first met at the 2013 World Sudoku Championship in Beijing, and have since become best friends — they have set the collective goal of together placing first and second at these events. Last year, in the playoffs, Mr. Vunk beat Ms. Dai by a mere eight seconds (he also won in 2016). Looking back, Dave Baines, an emerging technology researcher for the federal government and chair of the hosting Canadian team (the U.S.A. team co-hosted), praised it as “good theater.”
This year Ms. Dai came prepared to triumph; her performance optimization kit included twin plushies named Cinno and Doudou, earplugs, a halogen lamp mounted on a spare water bottle and an herbal oil for acuity and calm.
The Dai-Vunk rematch was highly anticipated, yet Kota Morinishi, 34, from Tokyo, a four-time world champion who works in information technology, took an early lead, fueled by a sack of candy ever on offer from his team captain.
Ms. Dai had a rough start: In Round 2 of 10 she made mistakes on, or “broke,” the same puzzle three times; ultimately she erased the whole thing and restarted. In Round 3, while focused on fixing two broken puzzles, she forgot a puzzle and didn’t complete it before time was up.
Mr. Vunk finished Round 3 with three minutes to spare — “Could’ve been better,” he said — putting him in first place, with Ms. Dai second.
Byron Calver, 38, a civil servant in Toronto who sat next to Ms. Dai, was not thrilled with his showing. (His best finish was fifth, in 2010, but he had practiced too hard and burned himself out, he said. Now, after a hiatus, he was trying recapture what he had lost: “Discovering your mortality by being bad at Sudoku, the Byron Calver story,” he said.) When asked how Round 4 had gone, he said, “It did not go.” It involved Sudokus with arithmetic constraints. “I did great at the math, I just forgot how to do Sudoku,” he said.
And at least once that day, in desperation, Mr. Calver resorted to a “wild bifurcation” — “bifurcation” being Sudoku-speak for “guess.” Typically, it is a calculated trial-and-error guess, exploring one of two clear paths presented by a partially completed puzzle. But in such an either-or gambit, only one path is correct. Mr. Calver’s bifurcation was more reckless, he said, “insofar as it was spurred more from blind hope in the absence of a clear path forward than from any well-grounded expectation that progress would result.”
At the outset of most rounds, Will Shortz, executive director of the 2023 World Sudoku and Puzzle Championships and chairman of the World Puzzle Federation, a nonprofit that supervises the event, stopped by the ballroom to collect the latest booklet and sometimes try a Sudoku or two. (He and Dr. Snyder underwrote the expenses for the W.S.P.C.)
Mr. Shortz has been the crossword editor at The New York Times since 1993, and is partial to word puzzles. He has a degree in “enigmatology” — a field of his own devising, although he said that the word could be found in 18th-century dictionaries, describing the study of riddles; he broadened the definition to include puzzles of all sorts. “We’re living in a golden age of puzzles right now,” he said in an interview before the event. “And it’s not only a golden age in interest in puzzles. It’s a golden age in invention and creativity in puzzles. I think it’s because more people use their brains now for their living than ever before.”
Mr. Shortz founded the World Puzzle Championship in New York in 1992; this is its 30th year. He crafted the competition to be “language and culture neutral, so everyone can compete equally,” he said. It features handmade logic puzzles in familiar genres: object placement, loop/path, shading, region division and number placement. (Sudoku, created by Howard Garns, originally called “Number Place” and first published in 1979, was occasionally included in the 1990s; after it became a craze, a dedicated World Sudoku Championship was established in 2006. The two championships were combined in 2011.)
Dr. Snyder, the Sudoku competition’s director, and Serkan Yurekli, a puzzle designer from Denizli, Turkey, and the director of the puzzle competition, worked long days with the organizing team for months leading up to the event, finalizing and checking hundreds of puzzles — “A puzzle feast,” Mr. Yurekli said.
Many competitors prefer logic puzzles to Sudokus for the variety of themes and rule sets, and “the kinds of deductions used to solve them,” said Walker Anderson, 22, a software developer at Art of Problem Solving, an online math education company in San Diego.
Chiel Beenhakker, 28, who works in retail data science analytics in Tilburg, Netherlands, said that more variety also meant “more intricacies to discover and make use of within puzzle types and more mixing and matching to your own specific solve strengths.” Mr. Beenhakker said he liked encountering new twists deployed by the competition’s puzzle authors and composing versions himself in order to figure out the mechanics and get in the zone. (The instruction booklet, containing samples, is provided in advance.)
“I enjoy puzzles more, but I’m better at Sudoku,” Mr. Beenhakker said; his gateway into this realm was the YouTube channel Cracking the Cryptic. Over the past couple of years, he has become good friends with Ms. Dai, and he can beat her at a single Sudoku, but in competition he tends to get distracted when stuck — he’ll stare at a puzzle too long, whereas Ms. Dai flips around in a booklet so as not to lose momentum. Her sustained high-level performance, and that of all top solvers, Mr. Beenhakker said, “blows my mind.”
At the start of Day 2 of the Sudoku competition, Ms. Dai and Mr. Vunk were tied for first place. They each solve using both a pen and a pencil, when certain and when guessing. Otherwise they have different styles and strategies. To prepare, Mr. Vunk might solve 20 to 30 puzzles a day, 50 to 70 daily on weekends; when a competition approaches, he eases off, tapering as he would before running a race. Ms. Dai solves intensively, say six to seven hours straight on a Saturday, to get ready for the pace of the competition. And she keeps practicing throughout the event, to warm up and keep limber.
Ms. Dai and Mr. Vunk were ranked first and second heading into the playoffs, with Mr. Morinishi in third and his Japanese teammate, Ken Endo, 30, a mechanical engineer, in the fourth spot. The competitors gathered in a room, sequestered from the audience; each had a camera trained on his or her clipboard, with live-feed video projected onto a screen in the ballroom. Ms. Dai’s point advantage going in earned her a 16-second head start on Mr. Vunk. She maintained her lead until the 10th and final puzzle.
“Those digits are going in fast, she might be onto something,” said Dr. Snyder, commenting on her homestretch progress. Shortly thereafter, Ms. Dai erased the entirety of her nearly complete grid. The audience gasped. She had tried a bifurcation but it hadn’t worked out. (“It didn’t contradict until the last few digits, so it seemed like I almost finished,” she said later.)
Dr. Snyder observed that Mr. Vunk seemed to be making poor choices: “He will also be in some pain soon.” Sure enough, out came his eraser. Ms. Dai proceeded to finish first, with Mr. Vunk second, four-and-a-half minutes later, followed by Mr. Kota in third, another four minutes behind.
(Japan won the Sudoku team title, and the United States won the puzzle team title. Mr. Endo won the individual puzzle championship, by a large margin, his third win; he also won the Sudoku title in 2019. Mr. Anderson and Thomas Luo, of Team U.S.A., placed second and third in the W.P.C.)
Overall, Dr. Snyder noted that the solvers’ idiosyncratic notations on the grids — memory cues and the like, beyond the basic method he used a decade ago — were “advancing the science of Sudoku,” allowing solvers to get faster and faster.
And then there is the hard-core scientific research. For her Ph.D., Ms. Dai is considering a problem inspired by a new paper posted online in October: “The linear system for Sudoku and a fractional completion threshold.” As she explained in an email, the question she plans to investigate is, “Given a super big n-by-n grid with some digits already filled, what conditions need to be satisfied by the given digits to guarantee a full completion solution to the Sudoku?”
Mr. Vunk, when asked if he followed the research, looked indifferent verging on perplexed. “No,” he said. “I just like solving.”