X-Wing

Vad är X-Wing?

An X‑wing is an advanced elimination technique used when a particular digit appears as a candidate in exactly two cells in two different rows (or columns), and those cells align perfectly in the same two columns (or rows). This forms an imaginary rectangle - and because the digit must go in one cell in each row/column, you can eliminate it as a candidate from other cells in the corresponding columns/rows.

This is a natural progression from naked pairs and builds on the foundation of naked singles and hidden singles. Make sure you're comfortable with these basic techniques before tackling X-Wing.

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Varför det är en spelväxlare

It's one of the first "fancy fish" techniques players learn, and for good reason. Once you spot one, you can remove misleading candidates and open up fresh possibilities - often triggering naked singles or hidden singles you couldn't see before. Think of it like clearing fog from a puzzle path.

Hur du hittar och tillämpar X-Wing (steg för steg)

  1. Bend your eyes to one digit - focus on, say, all the "7" candidates.
  2. Scan for exactly two candidates in two different rows (or columns).
  3. Check alignment - those candidate cells must line up in the same two columns (or rows).
  4. That creates a rectangle - that's your X‑wing. Whichever diagonal you pick (either or), the digit occupies one pair.
  5. Eliminate that digit from all other cells in the two columns (or rows) cutting through that rectangle.
  6. Watch for breakthroughs - new singles or cleaner candidate maps often pop up immediately.

Visuell genomgång

Imagine rows 4 and 8 both have exactly two "6" candidates - and they're both in columns 2 and 7. That forms a neat rectangle. Whether 6 is in (r4,c2) and (r8,c7) or in (r4,c7) and (r8,c2), you know both columns 2 and 7 must contain the six. So you can remove 6 as a candidate from any other cell in columns 2 and 7. That clean‑up often sparks progress.

Vanliga fallgropar och förväxlingar

  • Thinking any rectangle counts - not all 2‑by‑2 rectangles qualify. You need exactly two candidates in each row/column, and they must align.
  • Ignoring symmetry - it works in both directions: rows→eliminate in columns and columns→eliminate in rows.
  • Missing the logic - you're using disjunction: either diagonal placement A or B must happen, so candidates outside that pattern become impossible.
"X‑Wing is a candidate that, within 2 rows, only appears in 2 columns… it's not just a rectangle of cells you draw anywhere"

Bortom grunderna

  • Finned X‑wing: If one of the "corner" cells has extra candidates (a "fin"), you can analyze both possibilities (it's true vs. false) and eliminate candidates that fail in both scenarios.
  • Sashimi X‑wing: A distorted version where one corner doesn't align exactly - but the logic still applies through testing both configurations.

Both are powerful next‑level moves once you're comfy spotting classic X‑wings.

Varför X-Wing är viktigt

Once you internalize this pattern, your solving flow becomes smoother and more strategic. X‑wings help prune the candidate field in tricky mid‑to‑hard puzzles, and they lay the groundwork for even tougher "fish" techniques like swordfish, which is just a 3‑row/column version of X‑wing.

They're not just for puzzle show-off-ing - they genuinely speed up solving by forcing logic onto often messy sections of a grid.

Övningstips

  • After notes and singles stops working, shift your lens - scan all digits for 2-candidate rows or columns.
  • Use highlighting or shading if you can - it makes spotting rectangles way easier.
  • Once sweetly familiar, you'll start seeing X-wing setups pop out unbidden.

Sammanfattning

The X-wing is your first "fish" pattern - a smart, logical shortcut that lets you eliminate candidates from a distance, using only alignment and candidate counts. It's elegant, it's satisfying, and once you see one, your solver's instinct kicks into gear.

Redo att flyga vidare? Härnäst: XY-wing, när du är redo.

Vanliga frågor

Vad är X-Wing i Sudoku?

An X‑wing is an advanced elimination technique used when a particular digit appears as a candidate in exactly two cells in two different rows (or columns), and those cells align perfectly in the same two columns (or rows). This forms an imaginary rectangle - and because the digit must go in one cell in each row/column, you can eliminate it as a candidate from other cells in the corresponding columns/rows.

Hur tillämpar jag X-Wing?

To spot and apply an X-Wing: 1) Bend your eyes to one digit - focus on, say, all the "7" candidates, 2) Scan for exactly two candidates in two different rows (or columns), 3) Check alignment - those candidate cells must line up in the same two columns (or rows), 4) That creates a rectangle - that's your X‑wing, 5) Eliminate that digit from all other cells in the two columns (or rows) cutting through that rectangle.

Vad är skillnaden mellan X-Wing och andra tekniker?

X-Wing is one of the first "fancy fish" techniques players learn. It's different from basic techniques like naked singles because it lets you eliminate candidates from a distance using only alignment and candidate counts. It's more advanced than naked/hidden singles but simpler than techniques like Swordfish or XY-Wing.

När ska jag leta efter X-Wing-mönster?

Look for X-Wing patterns after notes and singles stop working. Shift your lens - scan all digits for 2-candidate rows or columns. Use highlighting or shading if you can - it makes spotting rectangles way easier. Once you're familiar with them, you'll start seeing X-wing setups pop out automatically.

Vilka varianter av X-Wing finns det?

Variations include: 1) Finned X‑wing - if one of the "corner" cells has extra candidates (a "fin"), you can analyze both possibilities and eliminate candidates that fail in both scenarios, 2) Sashimi X‑wing - a distorted version where one corner doesn't align exactly - but the logic still applies through testing both configurations.

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