Sudoku · EN
Sudoku X-Wing: Verified Worked Example
A row-based X-Wing uses a digit with exactly two candidate positions in each of two rows, in the same two columns. Those rows reserve the digit in those columns, so eliminate it from other rows in either column.
Solver-verified example
Starting grid; dots are empty cells.
Candidates before the move
- R1C7 = {2, 4, 5, 6}
- R1C9 = {2, 4, 5, 6}
- R4C7 = {1, 6}
- R4C9 = {1, 6, 9}
Work through this deduction
- Choose digit 6. In row 1 it can occupy only columns 7 and 9; row 4 has exactly the same two possible columns.
- Each of these rows must use 6 once. If the first row uses one column, the second must use the other, so these rows reserve the 6 in both columns.
- Remove 6 from row 6, column 9, outside the two base rows. It cannot share that column with either reserved 6.
- Do not choose the rectangle’s orientation yet. The four corner cells may have other, different notes; only the two positions for digit 6 in each base row matter.
Eliminate: R6C9 ≠ 6.
Independent verification found one completion. Forcing each displayed eliminated candidate separately produced zero completions. The grid and candidate pattern explain the move; the final answer is a check.
Verified completion
Why this deduction works
Whichever column takes the digit in the first row, the second row must use the other column. Both columns receive their copy from these two rows. Four corners alone are insufficient if a base row permits another position. Other notes in the corner cells do not need to match.
Sources and background
Frequently asked questions
Does this move finish the puzzle?
No. It establishes only the stated placement or eliminations. Update affected candidates and continue with another supported deduction.
Are incomplete notes sufficient?
No. Candidates must include every digit still permitted by the row, column and box. Missing a legal candidate can create a false pattern.
