MATLAB Sudoku Solver

Solves sudoku puzzles

Description

This is a recursive program that finds all possible solutions to a given sudoku puzzle. It's not the most efficient algorithm, but the entire function has less than 20 lines.

• MATLAB release: MATLAB 5.2 (R10)

[Ernold Blatford]

 

[mycsar norlie]

giler la

[Moe Zyslack]

some boring this program

[Jim Chang]

That is just awesome code! I wish I'd written it myself. SO COOL!

[Andrew Bliss]

See "MATLAB Sodoku Solver - Improved"

[Juha Haataja]

Elegant solution

[Jesper Oland]

Simpler:
% % Simple Recursive Solver % Programmed by Jesper Oland % spaceplant.com % function A = sudoku(A) if ~exist('A') % use this sudoku if none is given A=[0 1 0 0 0 0 0 7 0; 3 0 2 1 0 9 8 0 4; 0 0 0 5 0 8 0 0 0; 6 0 0 0 9 0 0 0 2; 0 4 0 0 0 0 0 3 0; 8 0 0 0 3 0 0 0 7; 0 0 0 9 0 5 0 0 0; 2 0 4 7 0 3 9 0 1; 0 9 0 0 0 0 0 4 0]; end [yy xx]=find(A==0); % find empty cells if length(xx)==0 disp('solution') disp(A); return end x=xx(1); y=yy(1); for i=1:9 % try 1 to 9 y1=1+3*floor((y-1)/3); % find 3x3 block x1=1+3*floor((x-1)/3); if ~( any(A(y,: )==i) | any(A(:,x)==i) | any(any(A(y1:y1+2,x1:x1+2)==i)) ) % if valid number tmp=A; tmp(y,x)=i; tmp=sudoku(tmp); % solve with this if all(all(tmp)) A=tmp; % solution return; % done end end end

[Jesper Oland]

http://www.sudoku.org.uk/discus/messages/5/105.html?1123204270

[Frank Diggelen]

I love this line:
if sum(M(i,:)==k)==0 & sum(M(:,j)==k)==0 & sum(mm(:)==k)==0 %OK for column, row, and 3x3 block

very elegant. Thanks

[Warren Hall]

Clean, crisp logic with a wonderful use of GUI. The solver does everything it claims with speed and precision.

[juan maria sandoval]

 

[Fahad Al Mahmood]

Works As Advertised! Thank you Geoff!

[Kate Chen]

very clver programming, but may get limitations if two many recursive step have to be taken

[Abhishek Dasgupta]

Lovely bit of coding ...

[Matthew Grimshaw]

Clever. I used this code with some additions (verification of the matrix, etc.) in a laboratory session teaching MATLAB to engineering students.

[J Taylor]

One single factor plays on my mind...what if it makes an incorrect guess? there is no way to make any sort of correction. or am i missing something?

[praveen alladi]

good,it is very helpfull

[Thomas Wichmann]

Generally a nice algorithm. However, it can be fooled by providing an incorrect starting matrix. For instance, it will "solve" the obviously incorrect matrix M:
M = [0,0,1,9,0,0,1,0,8;...
6,0,0,1,8,5,1,3,0;...
0,0,7,0,6,0,1,0,0;...
0,3,4,0,9,0,0,0,0;...
0,0,0,5,0,4,0,0,0;...
0,0,0,0,1,0,4,2,0;...
0,0,5,0,7,0,9,0,0;...
0,1,1,8,4,0,0,0,7;...
7,0,0,0,0,9,2,0,2];

[Vincent Cunningham]

Good program

[Peter Bone]

This will solve most easy Sudokus but not all. It doesn't check that a number must go in a particular box because it can't go in any of the other boxes in the row, col, square. Even if you included that it would not solve non-deterministic problems where you have to think several moves ahead. This can be done by guessing and then going back to the previous state if a contradiction is found.

[Felix Voigt]

The comment sent on 2007-02-05 is not correct. The algorithm will find ALL solutions to ALL non-contradictory Sudocu initial conditions. (Provided that your computer has enough processing power and you have enough time ...) By a recursive algorithm it consequently checks all possibilities for the 9 digits in non-occupied places of the 9x9 matrix, cancelling at configurations where two identical digits would be located in the same column or row or 3x3-square. So it finds ALL multiple solutions, in the case the initial conditions are to be solved in different ways. Wonderful.

[hi hi]

chung toi la chien si

[a nilu]

very good

[Olivier Planchon]

works fine. neat and pretty code. Comments are well appreciated.

[Husam Aldahiyat]

Excellent!

[Husam Aldahiyat]

 

[Wei Weimin]

Excellent.
http://www.truemark.cn/stegano/
An Information Hiding Scheme Using Sudoku.pdf