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Sudoku

What is Sudoku Puzzles?

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Sudoku is a logic-based number puzzle. Fill a 9×9 grid so every row, column, and 3×3 box contains digits 1–9 exactly once. A valid puzzle has exactly one solution. Sudoku requires no arithmetic — just logical deduction.

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How to Sudoku Puzzles

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1Naked singles: a cell can only contain one digit
2Hidden singles: a digit can only go in one cell within a row/column/box
3Naked pairs/triples: eliminate candidates from other cells
4Advanced: X-wings, swordfish, and coloring techniques

Worked Examples

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Example 1

Given:9×9 grid with seed numbers

Výsledok:Generates valid solvable puzzle or validates solution

Sudoku Difficulty Levels

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Level	Given clues	Techniques needed
Easy	36–50	Naked singles only
Medium	28–35	Hidden singles
Hard	22–27	Naked pairs, pointing pairs
Expert	17–21	X-wing, swordfish
Diabolical	17	Advanced forcing chains

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Pro Tip

Start by finding boxes, rows, or columns that already have 7–8 digits filled — the 9th is trivial. Look for digits that appear frequently in the given cells to quickly eliminate possibilities.

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Did you know?

Sudoku was invented by American architect Howard Garns in 1979 (as 'Number Place') and popularized in Japan in 1986 by Maki Kaji, who named it 'Sudoku' (a Japanese abbreviation of 'the digits must remain single'). It went global after appearing in British newspapers in 2004.

References

›Sudoku — Wikipedia