How to solve any puzzle using systematic logic — no guessing required.
Every QueenSweep puzzle has a unique solution that can be found through pure deduction. The difference between a beginner and a grandmaster isn't luck — it's knowing which techniques to apply and when.
This guide breaks down every strategy you need, organized into a repeatable solving method that works at every difficulty level.
That diagonal rule trips people up constantly. On a chess board, queens attack entire diagonals. In QueenSweep, only the four immediately adjacent diagonal cells are blocked. Two queens at (1,1) and (3,3) are perfectly legal — they're two squares apart.
The best solvers don't scan randomly — they cycle through four distinct phases. When one phase stalls, they move to the next. When any phase produces a result, they loop back to Phase 1.
Find every revealed 0 on the board and eliminate all 8 of its neighbors.
A zero means "no queens touch me." That's 8 cells you can mark with X immediately. On most puzzles, zeros cascade — eliminating neighbors of a 0 often completes constraints elsewhere on the board.
This single technique solves roughly 30–40% of a typical puzzle before you even think about anything else.
Work through every revealed number using two simple checks:
Count the flagged queens adjacent to a number. If the count matches the number, every remaining unknown neighbor is safe — mark them all with X.
Example: A 2 with two flagged queens nearby? Every other neighbor gets an X.
Count the unknown cells adjacent to a number, then subtract the queens already found. If the unknowns exactly equal the queens still needed, every unknown must be a queen.
Example: A 3 has 2 queens found and exactly 1 unknown neighbor left. That neighbor is guaranteed to be a queen. Flag it.
This is the bread and butter of QueenSweep solving. Run Check A and Check B on every number after each change to the board.
Every row needs exactly one queen. Every column needs exactly one queen. Use this.
The "Last One Standing" rule: If a row or column has only one unmarked cell remaining, that cell must be the queen. This is often the breakthrough that unlocks the rest of the puzzle.
The counting technique: Even before you're down to one cell, count the candidates in each row and column. Rows with only 2–3 candidates are high-value targets — they're most likely to become forced after the next queen placement.
Cross-referencing: When you place a queen, the game auto-marks its entire row and column. This frequently triggers a chain reaction — the row elimination removes a candidate from another column, which forces a queen there, which eliminates candidates in another row, and so on.
When Phases 1–3 stall out, you need lookahead — hypothetical reasoning.
Pick a row or column with the fewest remaining candidates (2 is ideal). Then:
What counts as a contradiction?
When two numbers share neighbors, their constraints interact. Look for cells that are adjacent to multiple unsatisfied numbers.
Example: Cell X is a neighbor of both a 1 (needs 1 more queen) and a 2 (needs 1 more queen). If X is the only shared unknown between them, the constraints narrow fast. If the 1 can only be satisfied by X, then X must be a queen — which also satisfies one of the 2's requirements.
When you flag a queen, the four adjacent diagonal cells get auto-eliminated. But think one step further: those eliminations affect which cells are available in neighboring rows and columns.
Place a queen at row 3, column 5. Now row 2 loses columns 4 and 6 as candidates. Row 4 also loses columns 4 and 6. If either of those rows was already down to 3 candidates, you might have just forced them down to 1.
On larger grids (8×8+), look at the distribution of remaining candidates across rows.
If you have three rows each with only 2 candidates, and those candidates share columns, the combinations are severely limited. Sometimes you can deduce that a specific column must have its queen in one of those contested rows, which forces placements in the others.
Think of it like Sudoku's "hidden pairs" — when two rows can only place queens in the same two columns, those columns are locked to those rows. No other row can use them.
The most powerful technique at Hard+ difficulty. Instead of testing one cell, trace a chain of forced consequences:
Therefore R3C2 is not a queen.
Longer chains are harder to hold in your head, but they're what separate Hard solvers from Grandmaster solvers. Start with 2-step chains and work up.
Instead of asking "where could the queen go?", ask "where can't it go?"
For each row, list what eliminates each cell:
Often you'll find that 6 out of 8 cells in a row are eliminated for different independent reasons, leaving you with only 2 candidates — a much easier what-if analysis.
Numbers on the edges and corners of the grid have fewer neighbors (5 for edges, 3 for corners). This makes their constraints tighter.
A corner 1 only has 3 neighbors. If you can eliminate just 2, the queen is forced. An edge 2 with 5 neighbors needs only 3 eliminations to become forced.
Here's the exact process top solvers follow:
The key insight: always return to Phase 1 after any progress. New eliminations cascade. A queen you just placed might complete a number constraint in Phase 2, which eliminates a cell in a different row, which forces that row's queen in Phase 3. Let the logic flow.
Queens at (2,2) and (4,4) are fine. Don't eliminate cells two squares away diagonally.
Don't guess. If you're not 100% certain a cell is a queen, don't flag it. Use Notes Mode to test theories. Wrong flags cost you on the mistake counter and can send your logic down the wrong path.
When you place a queen, the game marks its row, column, and adjacent diagonals. But it's easy to miss that these auto-marks just completed a number constraint elsewhere. After every queen placement, re-scan the board.
Don't solve row by row. Solve wherever the constraints are tightest. Jump to the row or column with the fewest candidates. Jump to the number closest to being satisfied. Let the puzzle guide you.
The status bar shows how many queens you've found vs. how many the grid needs. If you have 6 of 8 queens placed, only 2 rows and 2 columns still need them. The intersection of those rows and columns is a tiny search space.
Zeros and basic number crunching will solve the entire puzzle. Focus on building speed with Phases 1–3.
You'll hit points where no number is immediately solvable. This is where row/column accounting shines. Count candidates per row — the row with fewest candidates is your next target.
What-if analysis becomes essential. Start with rows that have exactly 2 candidates. Test one, propagate mentally, check for contradictions.
Multi-step chain reasoning. You may need to trace 3–5 forced moves before finding a contradiction. Notes Mode is your best friend. If you're tempted to guess, you're missing a deduction.
QueenSweep rewards systematic thinking over intuition. Every puzzle — from Beginner to Grandmaster — follows the same logic. The techniques don't change; they just stack.
Master the four phases, train yourself to see the cascading eliminations, and you'll find that puzzles which once felt impossible now unfold like dominoes.
Ready for more? The Advanced Techniques Guide illustrates six visual strategies with interactive mini boards.
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