How to use x wing in sudoku

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.

The Sudoku X-Wing pattern or technique is one of the most advanced techniques that can be applied to Sudoku puzzles from a medium difficulty level onwards. It is a very forthright method with a simply discernable pattern. It emphasizes one single digit, and its goal is to confine the number of cells that can have that number as a possible candidate. Sudoku X-Wing technique is also a valuable strategy for any player to learn as it branches out into more complex patterns and techniques that are required to solve impossible puzzles. In this article, I use one of my handcrafted, very difficult puzzles that have a known X-Wing pattern. Go ahead, download and print out this PDF very hard Sudoku puzzle 1. You will need to partially solve the puzzle to reach the picture shown.

How to use x wing in sudoku

Sign up for more. Main Page. Unsolvable Sudoku Unsolvable Jigsaw New! Unsolvable Str8ts. Print Version. X-Wing Strategy This strategy is looking at single numbers in rows and columns. It should be easier to spot in a game as we can concentrate on just one number at a time. What's special about them? Well, A and B are a locked pair of 7 s. So are C and D. They are locked because they are the only 7 's in rows B and F.

The first is a '2-Wing'.

The Sudoku X-Wing strategy is one of the most recurrent techniques that can be applied to Sudoku puzzles from a medium difficulty level onwards. It is a very straightforward technique with an easily identifiable pattern. It focuses on one single digit and its goal is to restrict the number of cells that can have that number as a possible candidate. Together with the Swordfish , the Sudoku-X-Wing technique is also a valuable strategy for any player to learn as it branches out into more complex patterns and techniques that are required to solve impossible puzzles. To be able to apply this technique, the player must find 2 rows or 2 columns where a single digit is a candidate in only two cells of each. These cells must be aligned by column and row, forming a square or rectangle when connected. The basic principle of this technique is simple.

This idea is completely analogous, logically, to pairs, triplets, etc. Here is the idea as an X wing : Consider any one candidate Consider any two distinct rows Let the candidate be limited to no more than two cells in each of these two rows Let this group of no more than 4 cells share exactly two columns The candidate is forbidden from all the cells in those two columns outside of those 4 cells Because of symmetry, one can exchange columns for rows in this rule. Note the following: All possible locations for 3's in row 9 are f9,h9. All possible locations for 3's in row 5 are f5,h5. Forbids 3 from f4,f8,h4,h6. To prove this technique, I prefer to use induction.

How to use x wing in sudoku

Love puzzles? Play Jigsaw Puzzles! New Game. Home How to Play. How to Play Contact us Sign in. Sudoku X Wing. Previous page. X Wing Take a look at row number 2 and row number 4 in this puzzle. Let's see which cells can contain the digit 8 in those two rows, they are highlighted in red. It happens to be that those 4 cells 2 in each row align up perfectly in the same two columns - column 5 and column 7.

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Let's see which cells can contain the digit 8 in those two rows, they are highlighted in red. Can you find the X Wing with the base of 8 in this puzzle? This is so much simpler than all those advanced strategies, so complex, which may or may not apply. Great pages and great explanation. Thank you. Is that correct? In each of these four boxes, the same pair of numbers appear. Hi Andrew, thank you for this extraordinary and marvellous site. The proposition works in some cases but not others. Congratulations on solving a very difficult Sudoku puzzle. Candidate Elimination After Using X-Wing Candidate Elimination Once you choose the cells containing the right numbers for your Sudoku logic using X-Wing, you can then remove the other existing cells with the same digits in their candidates. Updated on: November 19, X-Wing Strategy This strategy is looking at single numbers in rows and columns. Since they do, one of the requirements to apply this technique is not met.

The Sudoku X-Wing strategy is one of the most recurrent techniques that can be applied to Sudoku puzzles from a medium difficulty level onwards.

Unsolvable Str8ts. Take the first example, why go for ABCD? The rule is When there are only two possible cells for a value in each of two different rows, and these candidates lie also in the same columns, then all other candidates for this value in the columns can be eliminated. Nice graphics and good explanation. Therefor we can eliminate 8 from all other cells in this column - R5 C5 in particular. You'll often spot X-Wings - they are quite common, but they won't always lead to you being able to remove candidates. Let me illustrate. Once you choose the cells containing the right numbers for your Sudoku logic using X-Wing, you can then remove the other existing cells with the same digits in their candidates. The reverse is also true for 2 columns with 2 common rows. Here we see a row containing exactly two 4s: 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: Now if we think about this, we know that each of these rows has to have a 4, right? Once you've satisfied yourself that there aren't any easy methods you can apply to move forward, take a look at the candidate positions for 6, in rows 4 and 9. It seems to me that once applying the basic strategies yields no further change, usually there are only 2 or 3 candidates in each unresolved cell. Is it possible to solve this puzzle situation? The main difference is that the player cannot immediately eliminate the 3s from the rows connecting to the base pattern.