XV 數獨
5
9
3
4
3
2
5
1
7
9
4
7
4
3
6
2
5
8
6
3
5
7
4
4
8
7
3
9
3
7
2
8
6
1
3
9
2
8
單元格之間的X表示它們的和為10；V表示它們的和為5
什麼是 XV 數獨？
XV Sudoku（也稱為Ten-Five Sudoku）在相鄰單元格之間放置X和V標記。X表示兩個單元格的和為10；V表示它們的和為5。許多XV謎題使用負約束：缺少標記保證該對既不等於10也不等於5。結合標準數獨，這在整個網格中提供了非常緊密的約束。
一覽
| 約束類型 | 儲存格關係 |
| 典型給定數 | 18–24 |
| 難度評分 | ★★★☆☆ 3/5 |
| 平均解題時間 — 簡單 | 8分鐘 |
| 平均解題時間 — 中等 | 18分鐘 |
| 平均解題時間 — 困難 | 35分鐘 |
| 平均解題時間 — 專家 | 62分鐘 |
如何解 XV 數獨
| 技巧 | 它的作用 | 等級 |
|---|---|---|
| Negative Constraint | Where no X or V appears between adjacent cells, their sum is neither 10 nor 5. This eliminates (1,9), (2,8), (3,7), (4,6) for X and (1,4), (2,3) for V. | 進階 |
| Sum Pair Enumeration | List all digit pairs that sum to 10 (for X) or 5 (for V), then use row/column placement to identify which pair must occupy each marked pair. | 進階 |
| Marker Chain Logic | Multiple consecutive X and V markers in a row form a sum chain — enumerate valid assignments for the entire chain simultaneously. | 進階 |
| Box X-Interaction | An X pair forces both digits into specific positions within their shared box, constraining all remaining cells of that box. | 進階 |
平均解題時間
簡單
8分鐘
中等
18分鐘
困難
35分鐘
專家
62分鐘
常見問題
什麼是 XV Sudoku？
XV Sudoku is a variant where X and V symbols appear between adjacent cells. An X marks two cells that sum to 10. A V marks two cells that sum to 5. Standard Sudoku rules apply, and — critically — all X and V relationships are fully marked: if there is no symbol between two adjacent cells, those cells are guaranteed not to sum to either 10 or 5.
What pairs sum to 10 (X)?
The valid X pairs are: 1&9, 2&8, 3&7, 4&6. Note that 5&5 sums to 10 but standard Sudoku uniqueness rules prevent two 5s from being adjacent in most cases. The X constraint immediately limits each marked cell to a small set of candidates.
What pairs sum to 5 (V)?
The valid V pairs are: 1&4, 2&3. Only four digits can ever appear in a V cell: 1, 2, 3, or 4. This makes V markers particularly powerful for restricting candidates in the lower half of the digit range.
How does the no-symbol constraint work?
All X and V relationships are shown — if two adjacent cells have no symbol, their sum is guaranteed to be neither 5 nor 10. This negative constraint eliminates candidate pairs from unmarked cell boundaries and is often as useful as the explicit symbols.
Is XV Sudoku hard to learn?
The rules are simple to memorise. The challenge is applying both the positive (X, V) and negative (no symbol) constraints simultaneously across the entire grid. Easy puzzles are very accessible; expert puzzles require exhaustive tracking of all adjacent-cell relationships.
How long does XV Sudoku take to solve?
Easy puzzles take 8–15 minutes. Medium puzzles run 15–30 minutes. Hard puzzles average 30–60 minutes and expert puzzles often exceed 90 minutes. The no-symbol negative constraint is the most time-consuming to apply systematically across a densely marked grid.