奇偶数独
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
阴影单元格必须包含奇数数字；圆圈必须包含偶数数字
什么是奇数 / 偶数数独？
奇数/偶数数独将某些单元格标记为奇数（通常灰色阴影）或偶数（通常圆圈）。奇数单元格必须包含1、3、5、7、9中的一个，偶数单元格必须包含2、4、6、8中的一个。这立即将标记单元格的候选集减半，创造了强大的限制而不提供具体的数字。
一览
| 约束类型 | 单元格关系 |
| 典型给定数 | 20–26 |
| 难度评级 | ★★★☆☆ 3/5 |
| 平均解题时间 — 简单 | 6 分钟 |
| 平均解题时间 — 中等 | 14 分钟 |
| 平均解题时间 — 困难 | 28 分钟 |
| 平均解题时间 — 专家 | 50 分钟 |
如何解奇数 / 偶数数独
| 技巧 | 它的作用 | 级别 |
|---|---|---|
| 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. | 高级 |
| Parity Counting per Box | Count how many odd-marked and even-marked cells are in each box to verify the digit distribution is achievable. | 高级 |
| 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. | 高级 |
| Parity X-Wing | When parity restricts a digit to exactly two rows and two columns, form a parity-based X-Wing for cross-elimination. | 高级 |
平均解题时间
简单
6 分钟
中等
14 分钟
困难
28 分钟
专家
50 分钟
常见问题
什么是奇偶数独？
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.