Consecutive Sudoku – Hard

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Consecutive Sudoku, also known as "Successor Sudoku", "Sequential Sudoku", or "1-away Disallowed Number Place", is a variant of the classic Sudoku puzzle. In this variation, all cells where adjacent numbers are consecutive are specially marked, providing an additional clue as well as an extra challenge to the solver.

Basic Rules

1. Grid Structure: The puzzle consists of a 9x9 grid, divided into 9 smaller 3x3 grids.
2. Number Placement: Every row, column, and 3x3 grid must contain the numbers 1 through 9, with no repetition.
3. Consecutive Marking: Adjacent cells (horizontally or vertically) that contain consecutive numbers (e.g., 1 and 2, 2 and 3, etc.) are marked with a special symbol or shading.

Additional Rules

• Consecutive Indicator: The solver must pay attention to the marks indicating consecutive numbers, ensuring that the numbers placed in these cells are indeed consecutive.
• Non-Consecutive Cells: Cells without the consecutive marking must not contain consecutive numbers.

Basic Solving Tips

• Start with Certainties: Identify and fill in cells where a number can only go in one place, considering both the basic Sudoku rules and the consecutive markings.
• Use Pencil Marks: Utilize pencil marks for possible numbers in a cell and update them as you progress.
• Consecutive Chains: Look for chains of consecutive numbers that can help you determine the placement of other numbers.
• Avoidance: In areas without consecutive markings, ensure that you avoid placing consecutive numbers next to each other.