Medium Sandwich Sudoku
0
2
0
8
8
21
0
0
0
15
17
24
0
25
15
0
26
12
9
6
3
2
7
5
2
3
7
9
2
1
3
7
1
6
9
4
3
9
2
1
2
5
1
4
3
2
9
3
7
5
How to play Sandwich Sudoku
Standard Sudoku rules apply. The blue numbers on the left indicate the sum of digits sandwiched between 1 and 9 in that row. The blue numbers on top indicate the same for each column.
About Sandwich Sudoku
Difficulty
★★★★☆
4/5
Constraint Type
Outside Clues
Typical Givens
4–10 clue values
Avg. Solve (Medium)
26 min
Sandwich Sudoku places clues along the outside of the grid. Each clue gives the sum of all digits squeezed between the 1 and the 9 in that row or column. The positions of 1 and 9 vary, so the 'sandwich' can have 0 to 7 cells depending on where they land. A clue of 0 means 1 and 9 are adjacent. A clue of 35 means all digits 2–8 are between them.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Clue 0 Means Adjacent 1 and 9 | A sandwich clue of 0 means 1 and 9 are side-by-side with nothing between them. Place this pair immediately. | Beginner |
| Clue 35 Means 1 and 9 at Ends | A clue of 35 = 2+3+4+5+6+7+8. All middle digits are sandwiched, placing 1 and 9 at the two ends of the row/column. | Beginner |
| Position Enumeration | For each clue, enumerate all valid positions of 1 and 9 such that the enclosed digits sum to the clue. Cross-reference with column clues. | Intermediate |
| Sandwich Intersection | Row and column clues intersect at one cell. Combining row positions of 1 and 9 with column positions pinpoints key placements. | Advanced |
| Digit Forcing from Both Sides | Use clues from both the row and column sides to triangulate the positions of 1 and 9 simultaneously. | Intermediate |
Average Solve Time by Difficulty
Easy
12 min
Medium
26 min
Hard
52 min
Expert
85 min