Sinister Sudoku (25 page)

Row Seven has one space left, which is filled by 4
₇
.

STEP 12

For the next step, let’s start by looking at Row One, where a single remaining empty space takes 3
₄
. Column Four has three spaces left, which could take an 8, a 5, or a 4. Row Four, the topmost row with a blank in Column Four, already includes a 5 and a 4. That places 8
₈
. A 5 placed in the same box (one space to the right, two spaces down) eliminates all candidates but 4
₈
, placed as shown. That leaves 5
₇
in the bottom blank in the column.

Row Four now has a single blank space, which is filled by 3
₅
. Intersecting that space, Column Six now has only one blank, which is filled with 8
₉
.

Column Eight also has a single open space, leaving 3
₆
to fill it. That leads to a chain interaction with Row Five, where the last open space takes 5
₈
.

We’re almost down to the end now, so we have to take care.

STEP 13

Starting off lucky Step 13, let’s look at Row Nine, specifically, the intersection with Column Seven. Checking the bottom left and bottom center boxes, we find two 5s already placed. That forces the blank space to become 5
₉
. Similarly, in Row Eight, Column Five, existing 4s force the placement of 4
₉
. The blank space below, the last in Column Five, therefore becomes 3
₇
.

This leaves four spaces creating a sort of rectangle between Columns Seven and Nine and Rows Three and Eight, which can take either a 3 or a 1. If these last digits could be interchangeably placed, all our work goes for nothing—you don’t have a sudoku unless you have one unique solution.

Luckily, we have a single clue space left. That means we can force the placement of the remaining digits. Putting 1
₈
in the clue space fixes 3
₈
five spaces above. Then 1
₉
becomes the last space filled in Row Three, and 3
₉
completes the puzzle in Row Eight.

We did it! Here’s what the puzzle looks like with just the clues:

FINISHED PUZZLE

Try it and see whether your solution matches the chain of logic that went into developing the sudoku. Remember, though, if you want a hint, look in front of the puzzle—not in back!

And if you decide to try and create some more sudoku, just bear in mind—you may end up swearing just as much during the creating as you do in the solving.

However you decide to go, remember to have some fun along the way.

Puzzle from page 12

Puzzle from page 90

Puzzle from page 120

Puzzle from page 213