Jigsaw Sudoku – Hard

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Jigsaw Sudoku, also known as "Geometry Sudoku", "Geometry Number Place", "Irregular Sudoku", or "Kikagaku Nanpure", is a variant of the classic Sudoku puzzle. The primary distinguishing feature of this puzzle is the presence of irregularly shaped, non-rectangular areas, which replace the traditional 3x3 boxes found in standard Sudoku.

Basic Rules

1. Grid: The puzzle consists of a 9x9 grid.
2. Numbers: You must fill each cell of the grid with numbers from 1 to 9.
3. No Repetition: Each row, column, and outlined area must contain no repeated numbers from 1 to 9.

Additional Rules

• Irregular Areas: Unlike classic Sudoku, the 9x9 grid is divided into several irregularly shaped areas. Each of these areas must also contain the numbers 1 through 9 with no repetition.

Basic Solving Tips

• Unique Numbers: Ensure every row, column, and irregular area has unique numbers from 1-9.
• Avoid Repetition: Pay attention to avoid repeating numbers in each row, column, and irregular area.
• Use Pencil Marks: Employ pencil marks to keep track of possible numbers for each cell.
• Look for Certainties: Always place numbers that are certain first and then work on the probable ones.
• Check for Constraints: Ensure that the placement of a number doesn’t violate the basic Sudoku rules.
• Process of Elimination: Use the process of elimination to determine where numbers cannot go, thereby identifying where they can go.