Sudoku Puzzles #133, #134, #135, & #136

By: Dan LeKander

Volume 18, Issue 1, January 2023


You have already celebrated the start of 2023, so it is time to settle in and welcome a year of promise for Sudoku. We will continue with the 4 Sudoku puzzle format. So, let’s make this a great year for Sudoku growth!

Clueless?

We start with a Sudoku puzzle in progress, where it appears that there are no more obvious or not-so-obvious clues.  Can you find the hidden clue in Puzzle #133?

Puzzle #133

(The answer follows the conclusion of Puzzle #136, the feature puzzle for this month)

Logic Puzzle

Difficult rating … 8/10
(Rating based on puzzles not requiring advanced techniques)

Puzzle #134 should be fun and a bit of a challenge for you!

Puzzle #134

Impossible to solve?

Impossible?  No.  Difficult?  Yes.   Puzzle #135 should challenge you.  Advanced Techniques (Steps 6 and/or 7) are required.  If you solve this, you can consider yourself a master.

Puzzle #135

Feature Puzzle

Difficult rating …  3/10
(Rating based on puzzles requiring advanced techniques)

Puzzle #136

PUZZLE PREPARATION

Prior to utilizing techniques 1-8, complete the 5 Steps of Puzzle Preparation …

  1. FILL IN DATA FROM OBSERVATIONS
  2. FILL IN OBVIOUS ANSWERS
  3. FILL IN NOT-SO-OBVIOUS ANSWERS
  4. MARK UNSOLVED CELLS WITH OPTIONS THAT CANNOT EXIST IN THOSE CELLS
  5. FILL IN THE OPTIONS FOR THE UNSOLVED CELLS

The first thing we observe is that C8R2=7.  C5R7=8.
C4R8 & C5R8 have options 6 & 9.

C6R7, C6R8 & C6R9 are limited to options 1,2 & 7.

C6R3, C6R5 & C6R6 are now limited to options 3,4 & 5.

There is already a 4 & 5 in row 6; therefore, C6R6=3.  C6R3=5.  C6R6=3.  C8R4=4.

C5R7=8.

In box three a 9 can only exist as an option in C7R2 or C7R3; therefore, a 9 cannot exist as an option in C7R5, C7R6, C7R7 and C7R9.  Place a small 9 in the bottom of those cells to indicate this.

In box four a 7 can only exist as an option in C2R5 or C3R5; therefore, a 7 cannot exist as an op-tion in C4R5 and C5R5.

Now your grid should look like Example #136.1 below:

Example #136.1

This completes Puzzle Preparation Steps 1-4.  Next, we will fill in options for all unsolved cells, giving us Example #136.2 below:

Example #136.2

Dan recommends the following Steps to complete the puzzle.

Step 1:  Sudoku Pairs, Triplets and Quads – See September 2015
Step 2:  Turbos & Interaction – See October 2015
Step 3:  Sudoku Gordonian Rectangles and Polygons – See November 2015
Step 4:  XY-Wings & XYZ Wings – See December 2015
Step 5:  X-Wings – See January 2016

Step 6:  DAN’S YES/NO CHALLENGE
Step 7:  DAN’S CLOSE RELATIONSHIP CHALLENGE
Step 8:  AN EXPANSION OF STEP 7. Steps  1-5 are relatively common techniques and are explained in the TI LIFE articles. Steps 6-Posts 8 are covered in detail, in Dan’s book.

The first thing we notice is that there is a hidden pair in column 1.  C1R2 & C1R7 are the only two unsolved cells in column 1 that can have options 4 & 5.

Check row 1.  What do you see?  Yes, C4R1, C7R1, C8R1 & C9R1 form a quad with options 1, 2, 5 & 8; therefore, we can remove those options from the other unsolved cells in row 1.

Now, in box 3 a C7R1, C8R1 or C9R1 must be a 5, since no other unsolved cell in row 1 can be a 5; therefore, we can remove the 5 from C7R2.

Now your grid should look like Example #136.3 below:

Example #136.3

That completes techniques 1-5.  There are no Step 6 candidates, so we will move on to Step 7, Dan’s Close Relationship Challenge.

We will select C2R1 as our starter cell, with a sequence of 6,4.   We will annotate this on the 2nd level of this cell, as per Example #136.4 below:

Example #136.4

We annotate the unsolved cells that have a 6 as their option that are adjacent to the starter cell with “N6” indicating that those cells cannot be a 6 if the starting cell is a 6.  As we track the 4 through the puzzle, if any of these N6 cells is a value other than 6, it would indicate that this cell is not a 6 regardless if the starter cell is a 6 or 4, and the 6 could be deleted as an option for that cell.  We will track the 4 through the puzzle in Example #136.5 below:

Before we perform this exercise, we will list the potential outcomes …
• The tracking of the second number of the starter cell doesn’t reach the N9 cells, and there-fore, the exercise is unsuccessful.
• The tracking of the second number goes entirely through the puzzle without a conflict, in-dicating that the 2nd number is correct for the starter cell and you have solved the puzzle.
• The tracking of the second number creates a conflict, such as a number showing up twice in a row, column or box.   Or it could show up by having no cell for a particular number in a row, column or box.  Regardless of how the conflict arises, it would mean the second number is incorrect for that cell, and therefore, the answer to the starter cell is the first number.

Example 136.5

We will now track the 4 through the puzzle above on the third level of the unsolved cells to pre-serve the integrity of the original puzzle.

As you can see from example above, in tracking the 4 through the puzzle, we have reached an impasse.  Look at column 3.  No unsolved cell can be a 5.  That is a conflict.  So, now we know that C2R1 cannot be an 4; therefore, C2R1=6.

(Please note:  when you track the 4 through the puzzle you may find a different conflict.  Where the conflict occurs is dependent on how you track the 4.)
The puzzle is now easily solved, giving us Example #136.6 below:

Example #136.6

This feature puzzle is an example of being solved by just one Step 7 exercise.   More difficult puz-zles may require multiple Step 7 exercises to solve.

May the gentle winds of Sudoku be at your back.

By Dan LeKander


Clue for Puzzle #133 …  

Did you find the clue?  If not, read on.

Check row 1.  What do you see?

We see that C1R1, C4R1, C7R1, C8R1 & C9R1 cannot have options 3 & 9.  That leaves just two unsolved cells that can have options 3 & 9, which are C2R1 & C6R1. You have discovered a hidden pair, which will help you later in the puzzle.   Now your puzzle should look like Example #133.1 below:

Example #133.1

This should be a fun puzzle to complete.


Editor's Note: Hard to believe we are into 2023 and that our friend Dan LeKander has provided 4 more puzzles.  Looks like he will do so in the coming months - so your challenge Sudokus are alive and well.

Recently someone wrote to ask how to fill them out online. Unfortunately, you need to print them yourself - but that is easy to do and I know you will have just as much fun.

And, if you have not already done so, I suggest you purchase Dan’s book: “3 Advanced Sudoku Techniques, That Will Change Your Game Forever!” Purchase of a book includes a 50-page blank grid pad, 33 black and two green tokens. The book is available by contacting info@thousandislandslife.com.

Be sure to read the TI Life's review of Dan's book by Jesse Kahn published in Jun 2015.

Here are links to all past Sudoku Puzzle Challenge beginning: February 2016, March 2016, April 2016, May 2016, June 2016, July 2016, August 2016, September 2016, October 2016, November 2016, December 2016, January 2017, February 2017, March 2017, April 2017, May 2017, June 2017, July 2017, August 2017, September 2017, October 2017, November 2017, December 2017, January 2018, February 2018, March 2018, April 2018, May 2018, June 2018, July 2018, August 2018, September 2018, October 2018, November 2018, December 2018, January 2019, February 2019, March 2019, April 2019, May 2019, June 2019, July 2019, August 2019, September 2019, October 2019, November 2019, December 2019, January 2020, February 2020, April 2020, May 2020,  June 2020 and July 2020, August 2020,  September 2020, October 2020, November 2020 and December 2020, January 2021, February 2021, March 2021, April 2021, May 2021, June 2021, July 2021 , August 2021, September 2021 ,  October 2021, November 2021, December 2021, January 2022, February 2022, March 2022, April 2022 , May 2022, June 2022, July 2022 , August 2022, September 2022, October 2022, November 2022 and December 2022.

Posted in: Volume 18, Issue 1, January 2023, Sports, current


Please click here if you are unable to post your comment.


Submit an Article

Do you have an article you would like to submit? Click here to participate.