Expert Skyscraper Sudoku

Clues outside the grid count how many buildings are visible when looking in from that side (taller buildings block shorter ones).

Easy Medium Hard Expert

Expert Skyscraper Sudoku. Visibility forcing chains across rows and columns — the most demanding variant of the format. No guessing.

2
4
2
5
1
3
4
4
2
3
5
3
1
3
4
2
2
2
5
8
4
3
1
2
7
3
1
8
2
4
1
6
7
5
3
9
4
3
5
5
2
9
3
1
4
2
2
3
4
3
2
2
3
2
2
5
3
3
1
4
Mistakes
0/3
Score
-
Time
00:00
All Skyscraper Sudoku Puzzles →
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What is Skyscraper Sudoku?

Difficulty
★★★★☆
4/5
Constraint Type
Outside Clues
Typical Givens
4–10 clue values
Avg. Solve (Expert)
80 min

Solving Techniques for Expert Level

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
Want a full walkthrough of rules, strategies, and solving steps? How to Play Skyscraper Sudoku →

Frequently Asked Questions — Expert Skyscraper Sudoku

Is expert Skyscraper Sudoku solvable without guessing?
Yes. Every expert Skyscraper puzzle on Sudoku.by has a unique solution reachable through logical deduction. The permutation analysis required is extensive and the chains of reasoning are long, but every step follows necessarily from the constraints.
What strategies are unique to expert Skyscraper Sudoku?
Visibility forcing chains: assume digit 9 is in position P in row R. This fixes the row's visibility count, which may force the position of 8, which then determines a column's candidate set, which forces a digit in another row — and so on. Expert puzzles often require several such chains to find contradictions that eliminate starting assumptions.
How does the interaction between top/bottom and left/right clues differ at expert level?
At expert level, the mid-range clue values allow many individual row and column permutations. The key insight is that a cell constrained by both a mid-range row clue and a mid-range column clue often has a very small candidate set once all four edge clues (top, bottom, left, right) for that cell's row and column are applied together.
How many clues does an expert Skyscraper Sudoku have?
Expert Skyscraper puzzles have very few given digits inside the grid and the clues along all four edges. The outside clues all have mid-range values that individually allow many permutations — the puzzle's uniqueness comes from their combined effect across intersecting rows and columns.
How long does expert Skyscraper Sudoku take?
Expert Skyscraper Sudoku takes most players 60–120 minutes. If you are stuck, identify the row and column whose combined left/right or top/bottom clues have the fewest remaining valid permutations — systematically working from most-constrained to least-constrained is the most reliable path forward.

More questions? See the full Skyscraper Sudoku guide.