X-Wing
A digit's candidates in two rows line up in the same two columns. Remove that candidate from the rest of those columns.
In columns 5 and 7, candidate 2 appears only in rows 4 and 7. These 2 columns each need the digit once, with no two placements in the same row. The placements must therefore use all 2 rows. Remove candidate 2 from those rows outside columns 5 and 7.
What to look for
Choose a digit and find two rows where its only candidates are in the same two columns. The four positions form a rectangle.
Why it works
The digit must appear once in each row, in different columns. Those two placements use both columns, so no other cell in either column can contain the digit.
Try it step by step
- Find two rows where a digit has candidates in exactly the same two columns.
- Leave those four candidates in place.
- Remove the candidate from the two columns outside the selected rows. The same method works with rows and columns swapped.
Try it on a real puzzle
Start with the highlighted step, then keep solving. Use "Apply hint" to make the suggested change, or enter your own digits and candidate notes. Use "Undo" to reverse your last change.
| C1 | C2 | C3 | C4 | C5 | C6 | C7 | C8 | C9 | |
|---|---|---|---|---|---|---|---|---|---|
| R1 | |||||||||
| R2 | |||||||||
| R3 | |||||||||
| R4 | |||||||||
| R5 | |||||||||
| R6 | |||||||||
| R7 | |||||||||
| R8 | |||||||||
| R9 |
Use the arrow keys to move, 1-9 to enter a digit and Backspace or Delete to clear a cell. To add or remove a candidate, press C and then 1-9.
Source puzzle number: 327084 · Play this puzzle from the start
A simple example
If the only candidates for 7 in rows 2 and 6 are in columns 3 and 8, remove candidate 7 from those columns in every other row.
A house is a row, column or 3 × 3 box. A line is a row or column. Two cells "see" each other when they share a house. R1C3 means row 1, column 3. Boxes are numbered 1-9 from left to right and top to bottom. Braces such as {1, 2} show a cell's candidates, not confirmed digits.