Sudoku is a logic-based number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids contains all of the digits from 1 to 9.
Basic Rules:
- Fill in the grid so every row, column, and 3x3 box contains the digits 1 through 9.
- Each digit can only appear once in each row, column, and 3x3 box.
- The puzzle starts with some cells already filled in.
- Use logic to deduce the correct placement of numbers.
Solving Techniques:
- Scanning: Look for a digit that can only go in one place.
- Marking up: Note possible candidates for each empty cell.
- Elimination: Remove candidates based on existing placements.
- Look for patterns: X-Wing, Swordfish, and other advanced techniques.