Sudoku is a number-placement, combinatorial, logic puzzle. This genre traditionally features a 9x9 grid divided into 3x3 boxes, although sudoku can have dimensions of any composite number, divided into equally-sized, regular boxes. The objective of this genre is to insert the numbers 1-n (traditionally 1-9) into the grid so that each row, column and box contains one of each number in this range.


The objective is to fill in the numbers 1 to n in the grid, subject to the following rules:

  1. The numbers 1 to n appear once in each row and column.
  2. Each box also contains the numbers 1 to n.


A 9x9 sudoku and its solution

Sudoku Example

Sudoku Solution


Unless otherwise indicated, standard sudoku rules apply to all variants.

Irregular sudoku: A variant where the standard rectangular boxes are replaced by boxes of various shapes, each of which contain 1-n.

Windoku: In addition to the standard 3x3 areas of a 9x9, 4 more interior 3x3 boxes are included with each of these requiring the numbers 1-9.

Outside sudoku: Instead of clues entered into the grid, numbers are placed alongside a row or above/below a column indicating that a particular number appears within the first 3 cells, counting from the nearest edge.

Killer sudoku: Instead of clues entered into the grid, dashed boxes are included containing a selction of adjacent cells, indicating the total of all numbers within the selection.

Inequality sudoku: Inequality symbols appear between cells. These indicate the relative size between values of the two adjacent numbers.

Consecutive sudoku: In this variant, any two vertically or horizonally adjacent cells containing numbers with a difference of 1 are seperated with a bold line. As this affects all adjacent cells, the difference of the numbers in adjacent cells not seperated by a bold line must have a difference of at least 2.

Diagonal sudoku: Numbers from 1-n must appear in each marked diagonal in addition to each row, column and box.

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