The history of Sudoku

Sudoku looks Japanese, and its name is. But the puzzle has roots in 18th-century mathematics, in French newspapers and in an American puzzle magazine, before it went round the world in 2005.

1. 1782

   Latin squares

   A Latin square is a grid where each symbol appears once in every row and every column. The Swiss mathematician Leonhard Euler studied them in the 18th century, notably in his problem of the 36 officers. A finished Sudoku is a Latin square of order 9 with one more rule: each of its nine 3 × 3 boxes also holds every digit once.

2. 1892–1895

   Paris newspapers

   In 1892 the Paris daily Le Siècle published a partly filled 9 × 9 magic square, with 3 × 3 subsquares, to be completed by arithmetic. In 1895 its rival La France simplified it into a “diabolical magic square” (carré magique diabolique): each row, column and broken diagonal held the digits 1 to 9, and so, without being marked, did each 3 × 3 box. Such puzzles ran in French newspapers until about the First World War, then were forgotten.

3. 1979

   Number Place

   The modern puzzle appeared in the United States in 1979, in Dell's puzzle magazines, under the name Number Place. It was most likely designed by Howard Garns, a retired architect from Indiana, then 74. The rules were those of today: nine rows, nine columns, nine boxes, each digit once, and no arithmetic at all.

4. 1984

   Sudoku in Japan

   In April 1984 the Japanese publisher Nikoli brought it to Japan as “Sūji wa dokushin ni kagiru”, “the digits must stay single”. Its president, Maki Kaji, shortened the name to Sudoku: sū, digit, and doku, single. Nikoli's puzzles are made by hand, their clues usually placed symmetrically.

5. 2004–2005

   Around the world

   Wayne Gould, a retired New Zealand judge living in Hong Kong, came across a Sudoku in a Tokyo bookshop in 1997 and spent six years writing a program that makes them. The Times of London published its first on 12 November 2004. Other newspapers followed within weeks, then the rest of the world: 2005 was the year of Sudoku, in newspapers, in books and soon on phones.

6. 2006

   Championships

   The first World Sudoku Championship was held in Lucca, Italy, in 2006, and won by Jana Tylová of the Czech Republic. Since then the World Puzzle Federation has organised one nearly every year, with classic grids and many variants.

7. ∑

   The mathematics of the grid

   There are 6,670,903,752,021,072,936,960 ways to fill a Sudoku grid (Bertram Felgenhauer and Frazer Jarvis, 2005); 5,472,730,538 of them are really different, once rotations, reflections, relabelled digits and swapped rows or columns are set aside (Frazer Jarvis and Ed Russell). A puzzle with a single solution needs at least 17 clues: there is no Sudoku with 16, as Gary McGuire, Bastian Tugemann and Gilles Civario showed in 2012 by an exhaustive computer search.

8. Today

   The techniques

   Players worked out the logic of the puzzle together, naming its patterns as they found them: X-Wing, Swordfish, XY-Wing, coloring, chains. Every proper puzzle can be solved by reasoning alone; this site's technique pages show the ones My Sudoku uses, simplest first.

Sources: Wikipedia: Sudoku, Wikipedia: Mathematics of Sudoku, Wikipedia: World Sudoku Championship.

See the techniques