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Sudoku Puzzle Challenge–April 2016


April Sudoku Challenge brings you two puzzles that will test your Sudoku skills!

First, we will revisit the approach as discussed in Dan’s six TI LIFE articles …

DAN’S 8-STEP APPROACH TO SOLVING SUDOKU PUZZLES

Once you have completed the puzzle, to the extent that you have filled in all obvious answers and have written all potential options across the top of the unsolved cells (PUZZLE PREPARATION), Dan recommends the following steps to complete the puzzle …

2015/16 TI LIFE SUDOKU ARTICLES

Step 1:  Sudoku Pairs, Triplets and Quads – September, 2015

Step 2:  Turbos & Interaction – October, 2015

Step 3:  Sudoku Gordonian Rectangles and Polygons – November, 2015

Step 4:  XY-Wings & XYZ Wings – December, 2015

Step 5:  X-Wings – January, 2016

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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 per above. Steps 6-8 are covered in detail in Dan’s book.

Also see Sudoku Puzzle Challenge… February 2016, Sudoku Puzzle Challenge–March 2016

 

This eight step approach will solve virtually all published Sudoku puzzles. In my experiences in solving over 1500 puzzles, this approach has yet to fail. You may want to print this entire article to do the puzzles and have a “portable” guide to the solution, if needed.

PUZZLE #5 illustrates the importance of Puzzle Preparation. Please remember to search for obvious pairs in the Puzzle Preparation phase to save yourself time.

Puzzle 1 April

Puzzle #5

 

If you need assistance, Puzzle Preparation should result in the puzzle looking like below:

Puzzel 5 April second

PUZZLE #5 THRU PUZZLE PREPARATION

If your puzzle does not look like the one above, you probably missed something in Puzzle Preparation. If so, and you do not find the clue, then I suggest you continue with the above to see if you can reach a conclusion to Puzzle #5:

Steps to complete Puzzle #5:

  • The option 4, in C2R4 (column 2, row 4) & C2R5 form an Interaction in box 4, eliminating 4 as an option, in C3R4.
  • C1R5 & C3R4 create a Turbo, eliminating 3 as an option, in C7R9.
  • Cells C8R1, C8R7, C9R1 & C9R7 form a 1-sided Gordonian Rectangle. Either C8R7 or C9R7 must be a 4, eliminating the 4 as an option, from C3R7, C7R9 & C8R9.

From this point the puzzle is easily solved.

Puzzel 5 april completed

PUZZLE #5 COMPLETE

 

In the February & March 2016 issues of TI LIFE, Step 6, “DAN’S YES-NO CHALLENGE,” was used to solve puzzles #2 & #4. It is a fun technique and I would strongly suggest reading, the 16 pages devoted to this technique in my book. It explains in detail how to detect this Technique, when working on your Sudoku puzzles.

To keep the momentum moving forward, Puzzle 6 requires you to complete Steps 1-5 and then move on to Step 6. See if you can find two Step 6 techniques that will break the puzzle!

Puzzel 6 April

PUZZLE #6

 

If you need assistance, Puzzle Preparation should result in the puzzle looking like below:

Puzzell 6 2 april

PUZZLE #6 THROUGH PUZZLE PREPARATION

 

Again, if your puzzle does not look like the one above, you probably missed something in Puzzle Preparation.

If so, and you do not find the clue, then I suggest you continue with the above to see if you can reach a conclusion to Puzzle #6.

Steps to complete Puzzle #6:

  • C6R1 & C6R2 form an Interaction, eliminating 9 as an option from C6R6.
  • C7R1, C7R2 & C7R3 form an interaction, eliminating 6 as an option from C7R7 & C7R8.
  • C4R5 & C6R4 form a Turbo, in both directions, eliminating 1 as an option from C1R2 & C3R3.
  • C1R2, C1R7 & C3R9 form an XY-Wing, eliminating 4 as an option from C3R1 & C3R2.
  • C1R2 & C1R5 create a Dan’s Yes-No Challenge, eliminating 4 as an option from C7R2.
  • C8R2 & C8R8 create another Dan’s Yes-No Challenge, eliminating 4 as an option from C2R8.
  • C3R8 & C3R9 form an Interaction, eliminating 4 as an option from C3R4.

The puzzle is easily solved at this point.

Puzzel 6 3 april

PUZZLE #6 COMPLETE

If you have any questions or comments I would really like to hear from you. You can post on this TI Life issue, or contact me directly at djlsuniverse@yahoo.com. Do you work on the puzzles? Do the puzzles need to be easier or harder? Would you prefer a different format? Do you follow my suggested techniques, or do you solve the puzzles differently?

Thanks and see you next month!

By Dan LeKander, Wellesley Island, NY

 

Editor’s note:  Do you tackle a Sudoku on your cottage veranda, sailboat cockpit, or at a campsite?  TI Life is taking full advantage of Dan LeKander, from Wellesley Island, who is a Sudoku expert and author of “3 Advanced Sudoku Techniques – That Will Change Your Game Forever!”

In January 2016, we published a final article in his series – but many of us enjoy using “Dan’s Steps”, so when he asked if we would like a puzzle to solve every month … this editor said an enthusiastic… Yes, please!

I suggest you try this relatively easy puzzle and that you also purchase Dan’s book, “3 Advanced Sudoku Techniques, That Will Change Your Game Forever!”
Most importantly, I ask that you leave comments on any part of his series and throughout the coming year.  Remember when your teacher said –  no such thing as a silly question – as we can all learn together. 

Dan’s book is available at three locations online, (djlsuniverse.com, amazon.com and ebay.com).

Purchase of a book includes a 50-page blank grid pad, 33 black and two green tokens, to assist with Step 6.…

Dan LeKander and his wife, Peggy, have been seasonal residents of Fineview, on Wellesley Island, NY, since 1983.  In addition to being a Sudoku addict, Dan explores the 1000 Islands to enjoy the wildlife, beauty and of course, Catch-and Release bass fishing.

[See Jessy Kahn’s Book Review, “3 Advanced Sudoku Techniques…” by Dan LeKander, June issue of TI Life.]

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