Fill in each of the empty squares with the number 1, 2, or 3, taking care that no row or column contains any number (1, 2, or 3) more than once. (This isn't exactly like sudoku, but it does involve one of the constraints one must keep in mind.)
------------------------- | | | | | | 1 | | | | | | ------------------------- | | | | | 2 | | | | | | | ------------------------- | | | | | | | 3 | | | | | ------------------------- ------------------------- | | | | | 2 | | | | | | | ------------------------- | | | | | | 1 | | | | | | ------------------------- | | | | | | | 3 | | | | | ------------------------- ------------------------- | | | | | | 3 | | | | | | ------------------------- | | | | | | 1 | | | | | | ------------------------- | | | | | 3 | | | | | | | -------------------------