A 4x4 sudoku puzzle has 4 rows, 4 columns and 4 2x2 square regions, one in each corner. Can you create a 4x4 sudoku puzzle with only 4 clues given?

The most common sudoku variant is X-sudoku where the two main diagonals are two extra regions. Can you create a 4x4 X-sudoku puzzle with only 3 clues given?

Unless I'm mistaken, the following starting grid resolves to just one final solution. There are probably many that fit the first part, and there's also multiple ways of coming up with one for the second part.

1 . . .
. . . 2
. 4 . .
. . 3 .

1 2 . .
. . . 2
. 4 . .
. . 3 .

1 2 4 .
. . . 2
. 4 . . 
. . 3 .

1 2 4 3
. . . 2
. 4 . .
. . 3 .

1 2 4 3
. . 1 2
. 4 . .
. . 3 .

1 2 4 3
. 3 1 2
. 4 . .
. . 3 .

1 2 4 3
4 3 1 2
. 4 . .
. . 3 .

1 2 4 3
4 3 1 2
. 4 . .
. 1 3 .

1 2 4 3
4 3 1 2
. 4 2 .
. 1 3 .

1 2 4 3
4 3 1 2
3 4 2 .
. 1 3 .

1 2 4 3
4 3 1 2
3 4 2 1
. 1 3 .

1 2 4 3
4 3 1 2
3 4 2 1
2 1 3 .

1 2 4 3
4 3 1 2
3 4 2 1
2 1 3 4

Seems to me like the starting grid:

1 . . .
. . . 2
. 4 . .
. . 3 .

Can be solved to a unique solution.

As for the second part, the following is one way:

1 . . .
. 2 . 3
. . . .
. . . .

As it solves to:

1 3 4 2
4 2 1 3
2 4 3 1
3 1 2 4

Edited on March 19, 2007, 10:33 pm

Posted by Justin on 2007-03-19 22:33:04