After playing around with writing Sudoku Solvers in the past, I was interested to see this page which details a number of tiny sudoku solvers in a variety of languages such as Perl, Ruby, etc.
They have a few basic rules – no line over 80 bytes, etc, etc. And the examples take their input as a string of 81 digits, which represents the 9 rows of 9 digits, with “0″ being a blank square.
As I apparently have way too much time on my hands 
, I got up the motivation to convert one of these examples into Java. The results?
- The end program is around twice as many lines as the Perl original, and
- Yup – you can make Java programs as unreadable as anything else out there!
There may well be shorter possibilities out there – I didn’t put in a great deal of effort past converting the Perl original. But, for the record:
import java.util.*;public class S{static char[] A;static void R(){int i,j;for(i=
0;i<81;i++){if(A[i]!='0')continue;HashMap h=new HashMap();for(j=0;j<81;j++){h.
put(j/9==i/9||j%9==i%9||(j/27==i/27)&&((j%9/3)==(i%9/3))?""+A[j]:"0","1");}for(j
=1;j<=9;j++){if(h.get(""+j)==null){A[i]=(char)('0'+j);R();}}A[i]='0';return;}for
(i=0;i<81;i++){System.out.print(A[i]);}System.out.println();System.exit(0);}
public static void main(String[] a){A=a[0].toCharArray();R();}}
Assuming you have an appropriate classpath, you can run it with a line like:
java S 006070800000000000078601520030405010400000002090302060052103690000000000003020100
This code was converted from the excellent Perl example at:
http://www.ecclestoad.co.uk/blog/2005/06/02/sudoku_solver_in_three_lines_explained.html
