By the numbers: What it takes to wear the Sudoku crown

NEW YORK: On a mid-October Monday, 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 honours.

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.

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.

Dai and 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, Vunk beat 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 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.