Sudoku Solving

Sudoku (also known as "Number Place") is a placement puzzle. The puzzle is most frequently a 9 x 9 grid made up of 3 x 3 subgrids (called "regions"). Some cells already contain numbers, known as "givens". The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 exactly once. Each number in the solution therefore occurs only once in each of three "directions", hence the "single numbers" implied by the puzzle's name.

In some sudokus main diagonals also contain the digits 1 through 9. This variant is called "Diagonal Sudoku", Sudoku X or Kokonotsu. Use the check box Diagonals for such sudokus.

Also the puzzle may contain the regions of random (irregular) shape; this variant is called "Geometry Sudoku" ("Geometry Number Place"), Jigsaw or Kikagaku Nanpure:

Godoku (also known as Wordoku) is similar to sudoku, but uses letters instead of numbers. Once the grid is complete, the hidden word may be revealed.

In Asterisk Sudoku there is an additional area, shown on the grid by shading nine specially selected cells. Those nine cells must also contain 1 to 9.

Sudoku may contain additional four regions 3 x 3. This format was first introduced in the Dutch newspaper "NRC Handelsblad" by Peter Ritmeester. It is called Windoku (Four-Box Sudoku, Hyper Sudoku).

Sudoku-DG (also known as "Offset Sudoku") contains 9 disjoint groups in the puzzle, one for each relative box position. Each group has a distinct color. The group of 9 cells with the same color must also contain digits 1 through 9.

In Killer Sudoku, sub-regions have specified sums, and no number can be repeated within a region. This variant also called "Sums Sudoku" ("Sums Number Place").

Greater Than Sudoku is the variation of the original sudoku. In addition, greater than or less than signs (">" or "<") in the walls indicate that one cell's number is greater than or less than an adjacent cell's number.

Even-Odd Sudoku: fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. White cells must contain odd digits, gray cells must contain even digits.

In Consecutive Sudoku (or "1-away Disallowed Number Place"), all the places where orthogonally adjacent cells are consecutive numbers have been specially marked.

Sukaku ("Suuji Kakure"; also known as "Pencilmark Sudoku") has 81 groups of digits in a 9 x 9 grid. Like a standard Sudoku, the puzzle must be completed in such a way that each row, each column and each 3 x 3 box contains digits 1 through 9. Only the candidates shown in the grid can be used.

The program can solve the puzzles with the 12 x 12 grid (the subgrids' size is 4 x 3) and with the 16 x 16 grid (the subgrids' size is 4 x 4).

Samurai Sudoku is the variation of the original sudoku. The puzzle consists of five grids, one in the center and the other 4 overlapping each corner grid of the central one. This means that the numbers must be placed correctly for all the five puzzle squares.

Flower Sudoku has five sudoku puzzles in layout, similar to Samurai Sudoku. However, these puzzles overlap each other much more than in Samurai. The center grid is fully covered by the remaining four sub-puzzles.

Named for the warrior monks of medieval Japan, Sohei Sudoku has four merged grids. Each grid has two overlapping areas.

Kazaguruma ("Windmill Sudoku") consists of five grids, one in the center and the other 4 overlapping the central one. This means that the numbers must be placed correctly for all the five puzzle squares.

Butterfly Sudoku is the variation of the original sudoku. The puzzle consists of four grids 9 x 9. The numbers must be placed correctly for all the four puzzle squares.

Twodoku (also known as "Sensei Sudoku", "DoubleDoku") consists of two grids 9 x 9. The numbers must be placed correctly for both puzzle squares.