奇偶數獨
9
5
4
2
6
3
1
4
4
1
8
5
6
8
7
5
2
4
1
2
4
5
7
6
4
3
9
3
9
9
6
2
3
1
3
7
6
2
陰影儲存格必須包含奇數數字；圓圈必須包含偶數數字
什麼是 奇數 / 偶數數獨？
Odd/Even Sudoku 將某些單元格標記為奇數（通常灰色陰影）或偶數（通常圓圈）。奇數單元格必須包含 1, 3, 5, 7, 9 中的一個，偶數單元格必須包含 2, 4, 6, 8 中的一個。這立即將標記單元格的候選數集合減半，創造了強大的限制，而無需提供具體數字。
一覽
| 約束類型 | 儲存格關係 |
| 典型給定數 | 20–26 |
| 難度評分 | ★★★☆☆ 3/5 |
| 平均解題時間 — 簡單 | 6分鐘 |
| 平均解題時間 — 中等 | 14分鐘 |
| 平均解題時間 — 困難 | 28分鐘 |
| 平均解題時間 — 專家 | 50分鐘 |
如何解 奇數 / 偶數數獨
| 技巧 | 它的作用 | 等級 |
|---|---|---|
| Immediate Candidate Halving | Marked cells instantly reduce to 5 odd candidates (1,3,5,7,9) or 4 even candidates (2,4,6,8). Apply this before any other technique. | 進階 |
| Parity Counting per Box | Count how many odd-marked and even-marked cells are in each box to verify the digit distribution is achievable. | 進階 |
| Parity-Chain Elimination | If a row must contain exactly four even digits, and three positions are already even-marked, the fourth must come from the remaining unmarked cells. | 進階 |
| Parity X-Wing | When parity restricts a digit to exactly two rows and two columns, form a parity-based X-Wing for cross-elimination. | 進階 |
平均解題時間
簡單
6分鐘
中等
14分鐘
困難
28分鐘
專家
50分鐘
常見問題
什麼是 Odd/Even Sudoku？
Odd/Even Sudoku is a variant where some cells are shaded to indicate whether they must hold an odd or even digit. Purple-ringed cells must hold odd digits (1, 3, 5, 7, or 9). Yellow-shaded cells must hold even digits (2, 4, 6, or 8). Standard Sudoku rules apply to all cells.
What is parity in Sudoku?
Parity refers to whether a number is odd or even. In Odd/Even Sudoku, you can immediately halve the candidate list for any shaded cell. An odd cell can only hold 1, 3, 5, 7, or 9. An even cell can only hold 2, 4, 6, or 8. Combined with row, column, and box constraints, parity constraints make early placements much faster.
How do parity markings help solving?
Shaded cells eliminate half the digit range immediately. If a row already contains three odd digits and has an odd-marked cell remaining, that cell is heavily constrained. Counting odd vs even cells in each row, column, and box often reveals hidden singles that would be invisible without the parity markings.
Is Odd/Even Sudoku harder than regular Sudoku?
At easy and medium difficulty, it is comparable to or easier than classic Sudoku because parity markings provide immediate candidate reductions. Hard and expert Odd/Even puzzles use sparser markings and fewer given digits, making them comparable in difficulty to hard classic Sudoku.
What is the best first move in Odd/Even Sudoku?
Scan each row, column, and box and count how many odd and even slots remain versus how many odd and even digits are still unplaced. When only one cell in a row can hold an odd digit, that cell must contain an odd digit from the remaining candidates — this is a parity-based hidden single.
How long does Odd/Even Sudoku take to solve?
Easy puzzles take 5–15 minutes. Medium puzzles run 15–30 minutes. Hard puzzles average 30–60 minutes and expert puzzles can take 60–90 minutes. Parity-based hidden singles are the primary acceleration technique that distinguishes fast solvers.