Sudoku Puzzles #116, #117, & #118

By: Dan LeKander

Volume 17, Issue 8, August 2022

We continue with 3 puzzles each month.  Something for everyone!

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 #116?

Sudoku Puzzle #116

(The answer follows the conclusion of Puzzle #118, the feature puzzle for August)

Logic Puzzle

Difficult rating … 2/10
(Rating based on puzzles not requiring advanced techniques)

Puzzle #117 should be fun!

Puzzle #117

Feature Puzzle

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

Puzzle #118

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 7Steps  1-5 are relatively common techniques and are explained in the TI LIFE articles above. Steps 6-8 are covered in detail, in Dan’s book.



PUZZLE PREPARATION

Prior to utilizing Steps 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

We observe the following … C4R5=3.  C1R8=8.

C5R4 & C6R6 have options 5 & 6.  Then, C5R5 & C6R6 have options 8 & 9.

In box 7 a 3 can only exist as an option in C3R7 & C3R8; therefore, a 3 cannot exist as an option in in C3R1, C3R2, C3R4 & C3R6.

In box 7 a 6 can only exist as an option in C1R9 or C2R9; therefore, a 6 cannot exist as an option in C7R9 & C8R9.

In box 3 an 8 can only exist as an option in C8R1 & C8R2; therefore, a 8 cannot exist as an option in C8R4, C8R5, & C8R6.

Check out row 9.  Options 2 & 4 can only exist in C5R9 & C8R9.

Now your grid should like Example #118.1 below:

Example #118.1

This completes Puzzle Preparation Steps 1-4, but before we will fill in options for all unsolved cells, we will do a quick check for potential Step 6 exercises.

As in previous articles, we determined a particular number was a potential for a successful Step 6 exercise if that number appears as a given answer in 3 separate boxes, such that the boxes are not side-by-side, nor over each other.  Which numbers do you see that are good candidates?  Yes, 2 and 4.

We will first pick the number 2 and perform the exercise.  At this point at your home, you would put green tokens on two starter cells that are 2’s and black tokens on all unsolved cells that could have the option 2.  For purposed of illustration, in Example #118.2 below we will highlight two starter cells in green, and the unsolved cells that could be a 5 in yellow (vs black).

Example #118.2

We have chosen C5R9 & C8R9 as our starter cells.   We first assume C5R9 is the 2 and put a Y in that cell to indicate it is the 2 and see how it affects the yellow cells, placing a Y or N in the affected cells.

Next, we assume C8R9 is the 2 and place a y in that cell, and see how it affects the yellow cells, placing a y or n in those cells.

We can see that regardless of which starter cell is a 2, C1R3 and C5R1 cannot be a 2.     Also, re-gardless of which starter cell is the 2, C6R3 is a 2.   So C6R3=2.
By performing this exercise prior to filling in the options for the unsolved cells will give us some answers, reducing the amount of work filling in the option for the unsolved cells.  We now have Example #118.3 below:

Example #118.3

Now, in box 2 a 4 can only exist as an option in C5R2 & C6R2; therefore, a 4 cannot exist as an option in C1R2, C2R2 & C3R2.   Therefore, C2R3=4.  Then, C3R6=4, C8R5=4, C9R8=4, C5R9=4, C6R2=4, C5R7=2, C8R9=2, C9R4=2, C1R5=2, C3R1=2.

This puzzle is easily solved at this point, giving us Example #118.4 below:

Example #118.4

May the gentle winds of Sudoku be at your back.

By Dan LeKander, Wellesley Island

Clue for Puzzle #116 …  did you find the clue?  If not, read on.

Check column 6.  What do you see?

We see that C6R1, C6R2, C6R3 & C6R9 cannot be a 2 or 6; therefore, C6R5 & C6R8 must have options 2 & 6.  Then, C6R4=4.  Continue on and solve the puzzle!


Editor's Note:  Note: we went into the 100s in May 2022

Now here are Puzzles #116, #117, & #118

"I keep saying . . . when we published the final article in Dan's Series of steps to learn the logic of Sudoku, I never in a zillion years thought that Dan would so graciously offer to do one or two puzzles for us each month - and he has done so without my asking. Now we are up to 3!

Then his wife, Peggy, does the proof reading and I only have to post in on TI Life. We would love to know how many you have solved.  (Many, darn it, have stumped me, but I look forward to them each month.)

In May 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. and July 2022.

Please let this editor know how you did on this month's puzzles. I will report my status in September!

Posted in: Volume 17, Issue 8, August 2022, Sports, Communities, Current


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