FAQ on Sudoku

The most common Sudoku puzzles consist of a square divided into 81 frames; 9 columns by 9 rows. The large square is further organized into nine 3 by 3 areas. Initially, the grid is populated with a few solution values in order to help the solver discover and derive the values that are missing. To solve a Sudoku puzzle, the numbers 1 through 9 must be filled in within each column and row. Further, within each 3 by 3 sub-square, the numbers 1 through 9 must also appear. The grid has been solved when every square has been filled, and these three requirements have been met, in regard to the given values. When completed, each sub-square, column, and row of a traditional Sudoku add to the same number: 45.

Most sources credit Howard garns, a retired architect and puzzlemaker with creating the first modern Sudoku, published in 1979 by Dell Magazine as

. He died in 1989 before getting a chance to see his creation as a worldwide phenomenon.

In 1984,

, translated as “nanpure,” began running in a Japanese Magazine. The final name of Sudoku evolved as an abbreviation of the Japanese phrase, "suji wa dokushin ni kagiru" which means "the digits must occur only once.”

In 1997, Wayne Gould, a retired judge from the , came across

while visiting . He created a computer program which could generate new puzzles, and pitched the puzzles to the

Times

, which began running the puzzle in 2004. The puzzles quickly gained popularity, and were picked up by newspapers around the world.

Since 2004 the Sudoku craze has been sweeping the world, replacing publications’ traditional crosswords as the logic game of choice for most readers. Some puzzlemakers, seeing their crossword profits swirling down the drain, have ventured into the world of Sudoku, releasing puzzle books. Many crossword designers decry Sudoku as a cheap fad, as the puzzles are usually created by a computer program. Because of its incredible popularity, Sudoky has been called "The Rubik's Cube of the 21st Century."

The number of these hint solutions depends on the complexity of the puzzle. Fewer givens mean that more logic work must be done in order to fill in the grid. Easier puzzles usually have more values filled in at the beginning. Currently, mathematicians believe that the minimum number of given solution squares must be at least 17 in order for a puzzle to have a unique solution.

Modern Sudoku puzzles descend from Latin squares, a type of mathematical matrix with equal numbers of columns and rows. Sudoku style puzzles were published in French newspapers as early as the 1890s. Their solutions were based not on placement, but on deriving numbers which would cause each row and column to add to the same number. These early puzzles required math skills to solve, unlike modern Sudoku, in which the values of the numbers have no bearing on the solution to the puzzle.

The numbers 1-9 are used only because of their traditional association with Latin squares. In fact, colors, shapes, letters, or any other symbols could be used as values in a Sudoku puzzle.

Because Sudoku puzzles, unlike crosswords, are confined to a series of nine values in a 91 frame grid, and because of the three rules for completing a Sudoku, there is a finite number of possible puzzles. In 2005, mathematicians determined that 6,670,903,752,021,072,936,960 essentially different solutions are possible using a standard 9 by 9 Sudoku grid. When symmetries such as rotation, reflection and relabelling are taken into account, a mere 5,472,730,538 solutions are possible. If it takes an average of 15 minutes to solve a Sudoku puzzle, it would take well over 150,000 years to solve every possible 9 by 9 grid.

Since the start of the craze, hundreds of Sudoku puzzle books have been written, many enthusiast websites have been produced, and the puzzle has even become successful as a Nintendo video game. Links to more puzzles, and even Sudoku-solving tutorials can be found below.