Irregular Diagonal Sudoku
2
1
3
4
1
3
5
9
7
3
5
2
7
9
3
9
8
7
2
4
3
9
6
6
1
8
9
9
8
2
1
6
3
2
1
6
4
5
Mistakes
0/3
Score
-
Time
00:00
Progress0%
Easy · Irregular Diagonal Sudoku
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How to play Irregular Diagonal Sudoku
Each row, column, coloured region, and both main diagonals (highlighted in amber) must contain each of 1–9 exactly once. Regions replace the standard 3×3 boxes.
Full guide →
Combines jigsaw regions with main diagonal constraints
Easy
Irregular Diagonal Sudoku Easy
Medium
Irregular Diagonal Sudoku Medium
Hard
Irregular Diagonal Sudoku Hard
Expert
Irregular Diagonal Sudoku Expert
What is Irregular Diagonal Sudoku?
Irregular Diagonal Sudoku combines two variant types: the irregular jigsaw regions of Jigsaw Sudoku and the diagonal constraints of Diagonal Sudoku. Both main diagonals and all irregular regions must contain 1–9. The combination creates highly constrained puzzles with unique solving logic.
At a Glance
| Constraint type | Combined: Irregular + Diagonal |
| Typical givens | 22–30 |
| Difficulty rating | ★★★★☆ 4/5 |
| Avg. solve time — Easy | 8 min |
| Avg. solve time — Medium | 18 min |
| Avg. solve time — Hard | 35 min |
| Avg. solve time — Expert | 65 min |
How to Solve Irregular Diagonal Sudoku
| Technique | What it does | Level |
|---|---|---|
| Map All 29 Units First | You have 9 rows + 9 columns + 9 irregular regions + 2 diagonals = 29 constraint units. Identify all irregular regions and both diagonals before starting. | Beginner |
| Diagonal–Region Intersection | Cells on a diagonal that also sit in the same irregular region create a powerful two-unit intersection — use both constraints simultaneously. | Intermediate |
| Diagonal Pointing Pairs | If a digit on a diagonal is confined to one irregular region, eliminate it from all other cells of that region. | Intermediate |
| Region Coloring for Diagonals | Trace which irregular regions each diagonal passes through. Regions with many diagonal cells are the most constrained. | Advanced |
| Chain Deduction Across Units | With 29 units, a forced digit in one unit often cascades through 3–4 other units. Track chains carefully to avoid errors. | Advanced |
Average Solve Times
Easy
8 min
Medium
18 min
Hard
35 min
Expert
65 min
Frequently Asked Questions
What is Irregular Diagonal Sudoku?
Irregular Diagonal Sudoku combines two variants: irregular jigsaw-shaped regions replace the standard 3×3 boxes, and both main diagonals of the 9×9 grid must each contain 1–9 exactly once. Cells on a diagonal therefore belong to four groups: row, column, jigsaw region, and diagonal. It is one of the most constraint-dense variants available.
How many constraint groups does a diagonal cell belong to?
A cell on one of the main diagonals belongs to four groups simultaneously: its row, its column, its jigsaw region, and its diagonal. The centre cell belongs to five groups — both diagonals, plus row, column, and region. This extreme constraint density makes every placement very powerful.
Is Irregular Diagonal Sudoku the hardest variant?
It is among the most constrained variants. The combination of irregular regions and diagonal constraints means almost every cell interacts with an unusually large portion of the grid. Expert puzzles in this variant are among the most demanding logic puzzles on the site.
What order should I tackle the constraints?
Start with the diagonals, since diagonal cells carry the most constraints. Find hidden singles on each diagonal first. Then scan the jigsaw regions, keeping diagonal eliminations active. Update all four constraint groups — row, column, region, diagonal — after every single placement.
Can I use standard Sudoku techniques?
Yes — all standard techniques apply. You simply treat each diagonal as an additional house alongside the nine rows, nine columns, and nine jigsaw regions. The diagonal pointing pair (where a digit in a diagonal is confined to one row or column) is a particularly powerful technique unique to diagonal variants.
How long does Irregular Diagonal Sudoku take to solve?
Easy puzzles take 10–20 minutes. Medium puzzles run 20–40 minutes. Hard puzzles average 40–75 minutes and expert puzzles often exceed 90 minutes. The combined constraint density means that even easy puzzles require tracking four constraint groups simultaneously.