1. The Basic Rules of Sudoku
Sudoku is played on a 9x9 grid, which is divided into nine 3x3 smaller subgrids called "boxes".
- Each row must contain numbers 1 to 9 without repetition.
- Each column must contain numbers 1 to 9 without repetition.
- Each 3x3 box must contain numbers 1 to 9 without repetition.
2. Key Solving Techniques
Technique 1: Scanning & Elimination
Scan rows and columns to eliminate where a digit can go. If a row already contains a '5', no other empty cell in that row can be a '5'.
Technique 2: Naked Singles
Look at a single empty cell and list all numbers 1-9. Eliminate numbers that already exist in its row, column, or 3x3 box. If only one valid number remains, that is the cell's answer!
Technique 3: Using Pencil Notes
Use pencil notes to write candidate numbers in empty cells. As you fill numbers on the board, update and cross off pencil candidates.