Skyscrapers Solver Online

What is a Skyscrapers solver?

A Skyscrapers solver is an online tool that completes a Towers puzzle from the outside visibility clues and any known building heights. Each row and column must contain every height from 1 to the grid size exactly once.

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• Solve a Skyscrapers puzzle from a newspaper, app, book or printable sheet.
• Check whether your current entries are still possible.
• Reveal the next logical Skyscrapers move without showing the full answer.
• Test a handmade Towers puzzle for validity and uniqueness.

How to use this Skyscrapers solver

Choose the grid size first. In clue mode, click a number position around the outside of the grid and enter a visibility clue. In height mode, click an inner cell and enter any known building height.

Press Solve to complete the puzzle. Press Check to confirm that your entries can still fit a valid solution. Press Next move if you want a hint that shows candidates, highlights the useful cells and names the technique.

• Use 4x4 or 5x5 for quick Towers puzzles.
• Use 6x6 to 9x9 for larger skyline logic puzzles.
• Top clues look down a column; bottom clues look up a column.
• Left clues read a row from left to right; right clues read it from right to left.
• Apply a logical move only when you want the tool to update the grid.

Skyscrapers rules used by the solver

The solver uses the standard Skyscrapers rules. A 5x5 puzzle uses heights 1 to 5 in every row and column. A 7x7 puzzle uses heights 1 to 7. There are no boxes or regions.

The outside clues count visible buildings from one direction. A taller building hides every shorter building behind it, so the visible count rises only when a new maximum height appears in the line.

• Rows cannot repeat a height.
• Columns cannot repeat a height.
• A clue of 1 puts the tallest building on that edge.
• A clue equal to the grid size forces a rising sequence from that edge.
• Every filled number must stay within the grid range.

Next move logic and Skyscrapers strategies

The Next move helper starts with candidates. It removes heights already used in the same row or column, then compares the remaining line orders against the outside clues. If a height never appears in a cell across the valid skyline orders, it is removed.

After those eliminations, the helper looks for naked singles and hidden singles in rows and columns. It also handles direct clue logic such as clue 1 and full skyline clues before moving to broader candidate reasoning.

• Clue 1 places the tallest tower at the viewing edge.
• A clue of N fills the whole line as 1, 2, 3 ... N from that side.
• Skyline elimination removes heights that cannot satisfy the visible count.
• Naked singles place cells with one remaining candidate.
• Hidden singles find the only possible position for a height in a row or column.

Why a Skyscrapers puzzle may have no solution

A Towers puzzle can become impossible if a row or column repeats a height, if an outside clue cannot match any order, or if a clue and the given heights contradict one another.

A puzzle can also have multiple solutions. Published Skyscrapers puzzles normally aim for one answer, but a handmade grid with too few clues may allow several completed skylines. The solver checks for that and reports when the clues are not unique.