Medium Outside Sudoku
64
79
38
16
75
29
87
54
31
68
17
43
56
79
82
12
46
75
6
9
4
7
8
4
6
2
6
7
5
6
1
2
3
9
7
3
1
2
5
6
7
8
1
3
7
8
2
5
4
6
47
29
18
89
14
67
54
91
63
38
45
26
72
89
56
49
37
52
How to play Outside Sudoku
Standard Sudoku rules apply. Each digit shown outside the grid must appear within the first three cells of that row or column (the nearest 3×3 box). Blue clues on the left/right refer to the first/last three cells of that row; blue clues on the top/bottom refer to the first/last three cells of that column.
About Outside Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Outside Clues
Typical Givens
28–36 given + 4×9 outside clues
Avg. Solve (Medium)
18 min
Outside Sudoku places digits in the margins of the grid. Each outside digit must appear in one of the first three cells (the nearest box) of the row or column it points to. No standard given digits are provided inside the grid — all clues come from the margins. This creates an unusual form of Sudoku where the initial constraints come from outside the grid entirely.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Clue-Zone Mapping | Each outside digit must appear in the nearest 3 cells of its row or column. Map all outside clues to their zones immediately. | Beginner |
| Cross-Side Reasoning | If left clue digit X must be in cols 1–3, and right clue digit X is in the same row, that row already places X — the other side confirms its column. | Intermediate |
| Box-Side Interaction | An outside clue for a row interacts with the box containing cols 1–3. If the row's box is heavily constrained, the outside digit's position may be forced. | Intermediate |
| Digit Elimination from Clues | When a clue digit is placed in the zone, eliminate it from the rest of the zone row/col using standard Sudoku logic. | Intermediate |
| Dual-Side Chains | Combine left and right clues for the same row: both digits restrict the same three columns from opposite ends, leaving the middle box fully determined. | Advanced |
Average Solve Time by Difficulty
Easy
8 min
Medium
18 min
Hard
36 min
Expert
65 min