Place one of the four letters A, B, C or D in each of the bluecoloured cells. No letter can be horizontally or vertically adjacent to itself. The yellowcoloured tables above and to the left of the grid indicate how many times each letter appears in that column or row.
This is an extended version of ABCD.
               
    A  3  2  0  2  2  2  0  3  1   
    B  2  1  3  0  0  1  3  0  2   
    C  1  2  1  3  2  3  1  2  1   
 A  B  C  D  0  1  2  1  2  0  2  1  2   
 2  0  4  3            
 4  4  1  0            
 3  2  2  2            
 3  3  2  1            
 1  0  4  4            
 2  3  3  1            
               
Second attempt, with some brute force work!
A C D C A C D C D
B A B A C A B A B
A B D C A B C D A
B A B A D C B A C
C D C D C A D C D
A C B C D C D A B
Edited on March 8, 2008, 1:29 am

Posted by Dej Mar
on 20080307 13:37:36 