Expert Odd/Even Sudoku
5
9
7
1
4
8
9
9
3
7
5
6
9
8
6
2
4
5
4
1
2
7
2
3
7
3
6
How to play Odd/Even Sudoku
Standard Sudoku rules apply. Purple-ringed cells (odd) must contain 1, 3, 5, 7, or 9. Yellow cells (even) must contain 2, 4, 6, or 8. A wrong parity digit counts as a mistake.
About Odd / Even Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Cell Relationships
Typical Givens
20–26
Avg. Solve (Medium)
14 min
Odd/Even Sudoku marks certain cells as odd (often shaded grey) or even (often circled). Odd cells must contain one of 1, 3, 5, 7, 9 and even cells must contain one of 2, 4, 6, 8. This halves the candidate set for marked cells immediately, creating powerful restrictions without providing specific digits.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| 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. | Beginner |
| Parity Counting per Box | Count how many odd-marked and even-marked cells are in each box to verify the digit distribution is achievable. | Intermediate |
| 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. | Intermediate |
| Parity X-Wing | When parity restricts a digit to exactly two rows and two columns, form a parity-based X-Wing for cross-elimination. | Advanced |
Average Solve Time by Difficulty
Easy
6 min
Medium
14 min
Hard
28 min
Expert
50 min