Jigsaw sudoku puzzles are just like regular sudoku, except that the boxes have irregular shapes.
The irregular boxes fit toghether like the pieces of a jigsaw puzzle—hence the name.
Every jigsaw sudoku has boxes with different shapes and a different arrangement of the givens. Figuring out how all this plays together is what makes jigsaw sudoku fun!
For example, consider the 9s in the example above: There are only two of them, but the way the boxes are shaped lets us place two more 9s right away:
- Both R4 (row 4) and C2 (column 2) have 9s, so there has to be a 9 in R6C4, because that’s the only cell that can have a 9 in that box.
- In R5 there is only one cell where a 9 can be, since there already is a 9 both in C2 and the middle box.