Easy Skyscraper Sudoku
4
4
1
3
2
2
3
2
6
3
4
2
3
2
1
2
4
3
1
2
9
8
4
5
7
6
2
3
9
6
5
7
2
3
8
5
9
2
1
5
5
7
3
4
9
8
2
3
1
5
6
4
9
3
9
6
5
2
4
3
3
4
3
1
2
3
2
3
1
3
3
3
5
2
How to play Skyscraper Sudoku
Standard Sudoku rules apply. Each blue clue number tells you how many digits are visible looking into the grid from that edge - A digit is visible only if it is larger than all digits before it from that direction.
About Skyscraper Sudoku
Difficulty
★★★★☆
4/5
Constraint Type
Outside Clues
Typical Givens
4–10 clue values
Avg. Solve (Medium)
25 min
Skyscraper Sudoku imagines each digit as a building of that height. Clues outside the grid indicate how many buildings you can see looking from that edge inward — a taller building blocks all shorter buildings behind it. A clue of 1 means the first building must be a 9. A clue of 9 means the buildings are arranged in strictly increasing order (1,2,3,4,5,6,7,8,9). This variant requires both Sudoku logic and permutation reasoning.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Clue 1 Forces 9 First | A visibility clue of 1 means the first building from that edge must be a 9. All shorter buildings behind it are hidden. | Beginner |
| Clue 9 Forces Ascending Order | A clue of 9 means all buildings are visible, so digits are in strictly ascending order from that edge: 1, 2, 3, 4, 5, 6, 7, 8, 9. | Beginner |
| Permutation Enumeration | For each clue value V, enumerate all permutations of 1–9 that give exactly V visible buildings. Cross-reference opposite-edge clues. | Intermediate |
| 9 Always Visible | The digit 9 is always visible from either edge. The digit 8 is visible only if it appears before any 9 from that edge. | Intermediate |
| Multi-Edge Constraint | Combine the clue from one edge with the opposite edge's clue. Both must be simultaneously satisfiable. | Advanced |
Average Solve Time by Difficulty
Easy
12 min
Medium
25 min
Hard
50 min
Expert
80 min