Come Giocare a Killer Sudoku
Le gabbie devono sommare al totale dato — nessuna cifra si ripete all'interno di una gabbia
Killer Sudoku arrived in British newspapers in 2005, imported from Japan where it had quietly existed for years as "samunamupure" — sum number place. The Times printed one, readers revolted at how hard it was, and then kept demanding more. That tension is still the variant's signature: a killer grid usually gives you no digits at all, only dashed cages with little totals in the corner, and yet everything you need is sitting right there in the arithmetic. It suits two kinds of solvers especially well. If you love kakuro or mental maths, the cage combinations will feel like home. If you're a classic Sudoku player who has plateaued, killer forces you to learn genuinely new deductions — above all the 45 rule, which turns the fixed total of every row, column, and box into a scalpel. What separates killer from other arithmetic variants is the no-repeat rule inside cages: it shrinks combination lists dramatically, so the maths stays manageable even when the grid starts empty.
Le regole
Si applicano le regole standard del Sudoku: riempi ogni riga, colonna e box 3×3 con le cifre 1–9, ciascuna apparendo esattamente una volta.
Killer Sudoku sovrappone gabbie sulla griglia standard 9×9. Ogni gabbia è un gruppo di celle delineato da un bordo tratteggiato, con un piccolo numero nell'angolo che mostra la somma di tutte le cifre in quella gabbia. Le cifre non possono ripetersi all'interno di una gabbia. Nessuna cifra data standard appare nella griglia — tutti gli indizi provengono dalle somme delle gabbie. Killer Sudoku richiede sia logica Sudoku che ragionamento aritmetico, rendendolo una delle varianti di Sudoku più popolari e impegnative.
Per sapere da dove viene questo puzzle, come si confronta con varianti correlate e un riepilogo della strategia, consulta il nostro Killer Sudoku panoramica varianti.
A Colpo d'Occhio
Come Risolvere Killer Sudoku
Esempio Pratico: Aprire un Puzzle Killer Sudoku
Suppose the top-left box contains three complete cages: a three-cell cage totalling 15, a three-cell cage totalling 13, and a two-cell cage totalling 9 — eight cells accounted for, summing to 37. The box's nine cells must total 45, so the ninth cell, which belongs to a cage poking in from outside, is 45 − 37 = 8. One digit placed without a single given. Now look at that two-cell 9 cage: the 8 we just placed sits in a different cage but the same box, so the pair can't be {1,8} — only {2,7}, {3,6}, and {4,5} survive. Next, scan for a two-cell cage totalling 17 somewhere in the same band: it must be {8,9}, and since our box already holds its 8, the 17-cage's 8 fixes which row the band's remaining 8s avoid. This is the killer rhythm: a 45-rule deduction places a digit, the digit prunes a cage's combinations, the pruned cage behaves like a naked pair, and the eliminations set up the next 45-rule deduction one box over.
Errori Comuni in Killer Sudoku
| Errore | Come risolverlo |
|---|---|
| Ignoring the 45 rule and grinding cage combinations alone | Before enumerating anything, total the cages contained in each box, row, and column. The leftover innie or outie cell is pure profit — often a placed digit with zero combination work. |
| Forgetting the no-repeat rule when a cage crosses a box border | Digits can't repeat within a cage even where Sudoku rules alone would allow it. A four-cell cage totalling 26 can never be {9,9,4,4} — strike repeat-based combinations first and lists shrink fast. |
| Writing out every combination for big middle-value cages | A three-cell 15-cage has eight combinations; you'll drown. Start instead at the extremes — 2-cell cages of 3, 4, 16, 17 and 3-cell cages of 6, 7, 23, 24 — which have one or two combinations and anchor everything else. |
Domande Comuni
Cos'è il Killer Sudoku? ▾
Killer Sudoku combines standard Sudoku with arithmetic cage clues. The grid is divided into cages — groups of cells outlined by dashed borders — each with a small number in the corner. The digits in each cage must sum to that number, and no digit may repeat within a cage. Standard Sudoku rules also apply throughout.
What is the 45 Rule in Killer Sudoku? ▾
Every row, column, and 3×3 box contains the digits 1–9, which sum to 45. If you know the total of cages that sit entirely within a unit, you can deduce the sum of any partial cage cells crossing the boundary. These leftover cells are called 'innies' (inside the unit) or 'outies' (outside), and they often resolve to a single digit immediately.
Can I start solving without any given digits? ▾
Yes — Killer Sudoku typically has no pre-filled digits. All information comes from cage sums and Sudoku rules. Start with cages that have only one possible combination: a 2-cell cage summing to 3 can only be {1,2}, and a 2-cell cage summing to 17 can only be {8,9}. Apply the 45 Rule to each unit to find more placements.
How is Killer Sudoku different from Arrow Sudoku? ▾
In Killer Sudoku, digits within a cage must sum to the clue and cannot repeat within the cage. In Arrow Sudoku, digits along an arrow sum to the circle and can repeat. Killer cages are irregular shapes scattered across the grid; arrow cells follow a linear path from a circle.
Il Killer Sudoku è più difficile del Sudoku normale? ▾
Most players find Killer Sudoku harder than classic Sudoku at equivalent difficulty labels. Easy Killer puzzles are comparable to hard classic Sudoku. The arithmetic layer adds complexity, but cage constraints also provide more starting information than simple given digits once you learn to exploit them fully.
How long does Killer Sudoku take to solve? ▾
Easy puzzles take 10–20 minutes. Medium puzzles run 20–40 minutes. Hard puzzles average 40–75 minutes and expert puzzles often exceed 90 minutes. Applying the 45 Rule fluently is the single biggest factor in improving solve speed.