How to Play Skyscraper Sudoku

Outside clues show how many 'buildings' are visible from that edge

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The Rules

Standard Sudoku rules apply: fill every row, column, and 3×3 box with the digits 1–9, each appearing exactly once.

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.

At a Glance

4–10 clue values
Typical givens
Outside Clues
Constraint type
~12m
Easy solve time
~25m
Medium solve time

How to Solve Skyscraper Sudoku

Beginner
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.
Intermediate
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.
Advanced
Multi-Edge Constraint
Combine the clue from one edge with the opposite edge's clue. Both must be simultaneously satisfiable.
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Common Questions

When is a building 'visible'?

A building is visible if no taller building stands between it and the viewing edge.

Does 9 always count as visible?

Yes — 9 is always visible since it's the tallest building.

Do all rows and columns have clues?

Not necessarily — some positions outside the grid are blank, providing no constraint for that row or column.

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