Sudoku Solver

Make a copy/paste or type directly in cells. Letters (Wordoku/alphadoku) and digits are accepted.

Example: Copy the Sudoku content in the first cell (top left) 97 1 5 5 9 2 18 4 8 7 26 92 3 6 2 9 19 4572 to get :

Software solves the 9x9 sudoku like an human and display each step of its progress to understand.

Sometimes the reasoning stops at a step where no logical deduction can deduce at 100% the value of a box (several possible values). The solver performs a random pick among these possible values and continues, if an inconsistency occurs (the sudoku turns to have no solution) then it goes back to the step of the random pick and choose another value. To maximize the chances, choose a number which, if it is positioned in the cell, will allow the maximum of deduction in the continuation of the sudoku.

If the program indicates that there is only one possible value, it means that no other value is acceptable in the box.

dCode calculates all the solutions for the sudoku, not only the first one. To check a homemade sudoku, the solver can confirm that there is only one solution.

The first Sudoku versions are from 1979

A line can consist of $ 9! $ (Factorial of 9) different ways, but the whole sudoku has a number of possibilities much less than $ 9!^9 $, because some permutations can lead to identical grids. The total number of grids would be $ 9! \times 72^2 \times 27 \times 27 \times 704267971 = 6670903752021072936960 $ combinations.

By keeping the sudoku NxN rules that require the N characters to be used on each row and column, then it is impossible to respect them if the sudoku is not square.

Some variants of the square sudoku, however, use non-square inner blocks (see sudoku 6x6, sudoku 7x7 or sudoku 8x8)