In this advanced Sudoku strategy tips tutorial post I’ll be doing another example of where you can use the advanced X wing method to help you solve very hard Sudoku puzzles. You can also visit my previous post for more X wing column variation tutorials with examples.
Contents: Starting Sudoku Grid | Stuck on a Hard Sudoku? | Using the X wing Sudoku Strategy | More Advanced Sudoku Strategy Tips & Tutorials
Starting Sudoku Grid
In diagram 1 you will see the blank Sudoku grid used in this X wing tutorial.
Diagram 2 shows the cells I have managed to fill in the Sudoku grid – colored green. And also in diagram 2, you can see the cells where I am unable to find a definitive answer or number for the cell and so have noted the possible numbers that could be in the cells. If you unsure, how to play Sudoku, you may want to check out my previous post: Step by Step How to Solve Sudoku – Sudoku Tips and Rules.
However now that I have filled in all the cells of the grid in this very hard Sudoku example I am unable to continue the Sudoku puzzle using the simple method of deduction and elimination, so I must look for possible opportunities to use the advanced Sudoku strategy tricks. In this case, I’ll be using the X wing column variation technique.
Diagram 3, I have highlighted in yellow a possible opportunity of using the Xwing strategy. To check that the rules for the X wing technique can be applied, in this case to these 4 yellow cells, I must make sure that the number that I am going to apply the X wing method to, only appears in these 4 cells in each row. So for this example, I can see that the number 7, only appears in the 4 cells of rows 3 and 4. In other words, they make the 4 corners of a rectangle. So they do indeed make a case to use the X wing strategy. Remember that by applying the Sudoku rules, the 7 can only appear in one of the highlighted cells in rows 3 and 4. Similarly, the 7 can only be in one of the yellow cells in columns 3 and 9. And so, the 7 can only be in the opposite corners of this rectangle, hence making an X, i.e. an X wing formation.
Now that we have determined that this is an X wing, we know that there can be no other 7′s in the same columns i.e. columns 3 and 9 (the blue cells). So I can now remove the 7′s from my notations in these columns. As a result, this has immediately helped me to solve 3 more cells. First, the blue cell with the ’76′ notation can now be resolved to be 6. Similarly the blue cell with ’79′ notation can now be determined to be 9. Subsequently, the blue cell with the ’678′ notation, has to be ’8′. So using the X wing technique has enabled me to solve more cells, and should now help me move on with solving this Sudoku puzzle!
More Advanced Sudoku Tutorials
For more advanced Sudoku strategy tips and tricks with video tutorials and examples: