Quoted By:
It is impossible.
1. Start by filling out the center 3x3 with all 9 numbers in any order.
2. Now try to fill in the 3x3 that is one square above the center 3x3 (shown in blue). This requires the three numbers in the bottom row of the center 3x3.
3. Next, try to fill in the 3x3 that is one square right of the center 3x3 (shown in green). This requires the three of the numbers in the leftmost column of the center 3x3.
4. When you get to the 3x3 that is one square up and right of the center 3x3 (in purple), you are stumped. You need one number that is part of the union of the leftmost column and the bottom row of the center 3x3, but all of those have been used to fill in the 3x3s in steps 2 and 3. You cannot use any of those numbers because you would end up filling in either a 9-square row or a 9-square column with a repeated digit. Thus, your grid has GRIDS.
