Sudoku Puzzles #104, #105 & #106

By: Dan LeKander

Volume 17, Issue 4, April 2022

April is bonus month.  In addition to the “Clueless series” and feature puzzle, April will be the first month with a 3rd puzzle, a challenging Sudoku puzzle, but you will be able to solve it without advanced techniques. Let’s call it the “Logic series”, since Sudoku is a sport of pure logic.


As a bonus each month we start with a Sudoku puzzle in progress, where it appears there are no more obvious or not-so-obvious clues. Can you find the hidden clue in Puzzle #104?


Puzzle #104

(The answer follows after the conclusion of Puzzle #106, the feature puzzle for April)

Logic Puzzle

Puzzle #105 can be solved by just using logic versus needing advanced techniques. Since there can be only one answer for a valid puzzle, the answer will not be printed in the article.   You are on your own. Please enjoy.
Difficult rating … 5/10.

Puzzle #105

Puzzle #105

Feature Puzzle #106

Print this puzzle and give it a go.
Difficult rating … 7/10.

Puzzle # 106

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 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.

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


We will complete all of the first 4 steps in the order we observe them, until we conclude all Puzzle Preparation Step 1-4 clues.

The first thing we observe is that C1R8=6, C5R9=6 & C9R7=9.  C1R7 & C2R7 have options 2 & 3.  In box 1 a 4 can only exist as an option in C1R1 & C1R3; therefore, a 4 cannot exist as an option in C1R4, C1R5, & C1R6.  In box 5 a 9 can exist as an option only in C5R4 & C5R6; therefore, a 9 cannot exist as an option in C5R1, C5R2 & C5R3.

These clues give us Example #106.1 below:

Example #106.1

This concludes Puzzle Preparation steps 1-4, but before we move on to step 5 by filling in the options for all the unsolved cells, we will look at the puzzle and ask if there are any good Step 6 potentials. 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, there are no examples, so we will fill in the options for the unsolved cells, giving us Example #106.2 below:

Example 106.2

We will now proceed to Step 7, Dan’s Close Relationship Challenge.  As we have previously stated, all you need to qualify for a Step 7 exercise is at least one unsolved cell with just two options.  We will choose C6R4 as our “starter cell”, per example #106.3 below:

Example #106.3

We will pick a sequence for the starter cell C6R4 as 6,5, which we annotate on the 2nd level of this cell per Example #103.3 above.  We begin by asking ourselves that if this cell is actually a 6, what adjacent cells could not be a 6 and annotate those cells as “N6”, again on the 2nd level of the cells.

Next, we assume the starter cell is a 5 and track the results through the puzzle.  If any N6 cell is a number other than 6, it means that cell is not a 6 regardless if the starter cell is a 6 or 5, and the 6 could be eliminated as an option from that cell.

Before we perform this exercise, I will list the potential outcomes …

• The tracking of the second number of the starter cell doesn’t reach the N1 cells, and there-fore, the exercise is unsuccessful.
• The tracking of the second number goes entirely through the puzzle without a conflict, indicating 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.
We will now track the 5 through the puzzle above on the third level of the unsolved cells to pre-serve the integrity of the original puzzle.   You may want to track the puzzle also.  Please note column 7.  There is no unsolved cell that can be a 5.   (If there is a conflict, there will be many conflicts in rows, columns or boxes.  Please bear in mind that if you find a conflict, it may be in a different location than mine.)  What does this conflict tell us?  It tells us that the 5 in C6R4 can-not be the correct number, and that C6R4=6

The puzzle is easily solved from this point and the solution is Example #106.4 below:

Let’s pause here for a moment to ask ourselves the best way to select a starter cell.  You start by finding a 2-digit starting cell where one of the two numbers has a reasonable chance to track through the puzzle.  The 5 in C2R3 certainly seems it will track far.   Then you ask if the other number has at least two adjacent cells (in the same row, column or box) that have the same number as an option.   With a puzzle like this with three 2-digit option cells in the same column (a triplet), picking one of those cells as a starter cell almost guarantees that the second number of the starting sequence will track very well!

Solution Puzzle #106.4

May the gentle winds of Sudoku be at your back.

By Dan LeKander

[Author's note: Clue for Puzzle #104 …  did you find the clue?  If not, read on. Take a look at column 6.   What do you see?

Only two unsolved cells can have option 2 & 6.  

So, mark C6R5 and C6R8 as options 2/6.   Now, a 4 can only exist in one unsolved cell in column 6, which is C6R4.   C6R4=4.]

Editor's Note:  April 2022 - into the 100s

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 with this being numbers #104,105,& 106. What can I say . . . you Dan and your wonderful proofreader, Peggy are amazing.  Just look at the list below to prove it!

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 online at

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 and March 2022.

Posted in: Volume 17, Issue 4, April 2022, Sports

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