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X- Wing Sudoku technique | Master Sudoku: From Beginner to Expert - Class 1 PDF Download

X Wing

An X Wing is a technique for removing candidates (pencil marks).
It starts with either two parallel rows or two parallel columns. Blocks are not involved here.

  • If you can find a row that contains the same pencil mark in exactly two spots, as well as another parallel row that mirrors it.
  • Containing the same pencil mark in only the same two spots, then you can use this information to eliminate similar pencil marks in the columns passing through those spots.

I know…that's a mouthful. Let me illustrate. Here we see a row containing exactly two 4s:

X- Wing Sudoku technique | Master Sudoku: From Beginner to Expert - Class 1

Next, if we zoom out a bit, we can see that another row, two rows down, has the same two 4s, and in the same two spots:
X- Wing Sudoku technique | Master Sudoku: From Beginner to Expert - Class 1

Now if we think about this, we know that each of these rows has to have a 4, right?

  • And we also know the 4s cannot be on top of each other, because that would put two 4s in the same column.
  • Because of this, we can safely assume that either the light blue cells or the dark blue cells must be 4s.
  • Armed with this, let's zoom out all the way and shift our focus to the columns involved here (indicated with arrows below). Based on what we said above, the 4s in these columns must exist where these two rows cross - that is, where the blue 4s are.
  • Knowing that, all other 4s in the columns are not possible, and can be erased (erase all the pink 4s).
  • X- Wing Sudoku technique | Master Sudoku: From Beginner to Expert - Class 1Again, this is one of those hard to find methods. In Sudoklue, the same pencil mark highlighting feature that helps me find hidden singles and omissions, can make X Wings easier to spot as well.

Of course, this whole concept can be rotated. If you can find two columns with only two identical positions for a given pencil mark, then the corresponding rows intersecting these positions can have all other candidates safely removed.

The document X- Wing Sudoku technique | Master Sudoku: From Beginner to Expert - Class 1 is a part of the Class 1 Course Master Sudoku: From Beginner to Expert.
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FAQs on X- Wing Sudoku technique - Master Sudoku: From Beginner to Expert - Class 1

1. What is the X-Wing technique in Sudoku?
Ans. The X-Wing technique is an advanced solving method used in Sudoku puzzles. It involves identifying a specific pattern of candidate numbers in two rows and two columns that form a rectangle. If a certain number appears in exactly two cells of each row and these cells align with the same columns, the candidate can be eliminated from other cells in those columns.
2. How do I identify an X-Wing pattern in a Sudoku puzzle?
Ans. To identify an X-Wing pattern, first look for a candidate number that appears exactly twice in two different rows. Next, check if these occurrences align in two columns. If you find this arrangement, you've identified an X-Wing. You can then eliminate that candidate from any other cells in those two columns outside the identified rows.
3. Can the X-Wing technique be used in all Sudoku puzzles?
Ans. The X-Wing technique can be applied in medium to hard Sudoku puzzles where the candidate numbers are not easily deduced. However, it may not be necessary or useful in simpler puzzles, as they can be solved using basic techniques such as scanning or cross-hatching.
4. What are some common mistakes when using the X-Wing technique?
Ans. Common mistakes include misidentifying the X-Wing pattern, as it requires precise alignment of candidate numbers. Another mistake is forgetting to eliminate candidates from the relevant columns after identifying the X-Wing, which can lead to incorrect conclusions about the puzzle's solution.
5. How can I practice the X-Wing technique effectively?
Ans. To practice the X-Wing technique, start with Sudoku puzzles labeled as 'medium' or 'hard.' Look specifically for patterns involving two rows and two columns. Online Sudoku platforms often allow you to test your skills with hints and solutions, which can help reinforce your understanding of the technique.
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