What rules must be followed when solving a Sudoku puzzle?

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To solve a standard 9×9 Sudoku puzzle, you must fill the empty squares in the grid by following these logical rules:

Each row must contain all the numbers from 1 to 9 exactly once.1
Each column must contain all the numbers from 1 to 9 exactly once.1
Each of the nine 3×3 subgrids must contain all the numbers from 1 to 9 exactly once.1

It is important to note that Sudoku is based entirely on logic rather than arithmetic; the goal is simply to ensure that each number remains "single" within its respective row, column, and subgrid. While various complex variations exist—such as those involving diagonals or specific sums—the fundamental objective remains the same: placing the correct numbers to satisfy these constraints.1