Sudoku 8×8 – Hard

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Sudoku is a classic logic puzzle that comes in various grid sizes, with the 8x8 variant being one of them. In the 8x8 Sudoku, the grid is smaller than the standard 9x9 version but still provides a compelling and challenging puzzle. The grid is divided into smaller regions, and the solver must fill in missing numbers according to specific rules.

Basic Rules

1. Grid Structure: The puzzle consists of an 8x8 grid, which is further divided into 4x2 subgrids (regions).
2. Pre-filled Numbers: Some cells in the grid are pre-filled with numbers from 1 to 8.
3. Objective: The solver must fill in the empty cells with numbers, adhering to specific constraints.

Additional Rules

1. Number Usage: Use only numbers 1 through 8.
2. Unique Numbers: Each number from 1 to 8 must appear exactly once in each row, column, and region.

Basic Solving Tips

1. Single Possibility: If a cell is the only one in its row, column, or region that can contain a particular number, then it must contain that number.
2. Exclusion: If a number is already present in a row or column, look to place that number in other regions in the same row or column where it is not present.
3. Double Pairs: If you find two cells in a row, column, or region that can only be two numbers (like 3 and 6), then exclude these two numbers from other cells in that area.
4. Look for Grid Symmetry: Sometimes, the arrangement of given numbers has a symmetrical pattern that can help predict the placement of other numbers.