10/7/2023 0 Comments Xyz wing sudoku strategyX-Wing is not a strategy to enter a digit in the indicated cells but rather a way to eliminate a digit elsewhere on the grid. If you can wrap your head around this method, you'll start to develop ways of thinking that will allow you to pick up the rest of the strategies. The first advanced strategy to learn is X-Wing. If you progress beyond the easy and easy-intermediate stage, you will discover that there is an elegance and poetry to solving Sudoku that goes beyond mere counting and filling in the missing digit. The second is to teach some advanced methods for solving Sudoku. The first is to confound the programmers and get you to actually solve these the way they are supposed to be solved. This is the beginning of a series of puzzles that have two goals. If you've been paying attention to my previous puzzles, you'll know that I disapprove of such measures. They'd rather run write a computer program and let it fill in the blanks. The dark side is that some people don't want to solve the puzzle. Why not? All you have to do is solve a straight-forward Sudoku puzzle, grab the digits, and plug them into the coordinates. If this post needs further clarification please let me know.Puzzle cachers just LOVE Sudoku (although the craze may have passed). Quite simply, I have yet to find an easy way of spotting an x-wing without simply identifying four squares in a rectangular pattern and at most two 3x3 boxes that each have the same 2 possible numbers. Notice also that each of the locations highlighted in the original answer are in separate 3x3 boxes and may be solvable within those boxes. I recognize that this post is more complicated than the previous answer, but it is important to note that when identifying x-wings more than one number must be involved in order for it to actually be a standstill/unsolvable situation I have circled some of the other numbers involved in the x-wing predicament in the following image. So in either of the cases where the combos are 3&9 or 8&9 in the boxes, the x-wing forms (think about it - an x is made up of two lines) and the puzzles become unsolvable. The trick is that two different numbers are possible in each box involved in the x-wing (not just one, as the previous answer supposed - then, it may still become the only possible number, which is a crucial solving technique in sudoku). The issue is not only in the 'x-wing' shown before, but also in the three lowest boxes (7-9) in the shown columns 3 and 5. I am rehashing this question because I was going through some historical and it was poorly answered and understood before. Computers have no problem spotting them, of course. There can also be an X-Wing involving a row and a 3x3 box, but they are even more difficult to see. It is even more difficult to find 3 numbers in 3 rows/columns, or 4, etc. You'd have to look for 2 numbers occurring in 2 rows or columns. I usually don't look for them when solving with pen & paper. Imo, X-Wings are not easy to spot without highlighting all occurrences of a number. But then, for rows 3 and 8 to both contain a 9, Both B and D would have to be 9 and this is not possible, because then column 5 would have two 9's. ![]() If this were a 9, then A and C cannot be 9. ![]() ![]() Try making any of the red ones a 9, for instance row 1, column 3. So any 9's in these squares can be deleted. This means that any other squares in the same column as these squares can NOT be 9. In either case, these 4 squares will provide the 9's for rows 3 and 8, and because of that, they will also provide the 9's for their columns (3 and 5). Since every row must contain exactly one 9, either A and D must both be 9 OR B and C must both be 9. ![]() See how's there's two 9's in row 3 and also two 9's in row 8? (highlighted in blue) I've highlighted the X-Wing and the 9's involved in this X-Wing:
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