Flower Sudoku – Medium

Flower Sudoku

Flower Sudoku is a multi Sudoku puzzle. This means: the puzzle isn't just a single classic Sudoku, but several interconnected 9x9 Sudokus. Each sub-Sudoku follows the normal Sudoku rules: each row, each column, and each 3x3 block must contain the numbers 1 to 9 exactly once.

Flower Sudoku is a blossom-like multi Sudoku form. Several classic 9x9 Sudokus overlap to create a compact overall shape. The center is particularly well connected.

In Flower Sudoku, the shared areas are especially valuable because a central entry can influence multiple surrounding sub-Sudokus simultaneously. Like all Sudokus, no calculations are needed. The numbers are symbols placed correctly through logical elimination.

Basic Rules

• The puzzle consists of several classic 9x9 Sudokus connected into a common figure.
• Exactly one number from 1 to 9 is entered into each active cell.
• Within each 9x9 Sudoku, each row must contain the numbers 1 to 9 exactly once.
• Within each 9x9 Sudoku, each column must contain the numbers 1 to 9 exactly once.
• Within each 9x9 Sudoku, each 3x3 block must contain the numbers 1 to 9 exactly once.
• Shared cells belong to multiple sub-Sudokus. The entered value is the same for all involved sub-Sudokus.
• Given numbers may not be changed.
• Empty areas outside the visible grid do not belong to the puzzle and are not filled in.
• A multi Sudoku is solved when every included 9x9 Sudoku is correctly solved and all shared cells match.
• Important: a long visible row does not automatically mean a Sudoku row. The boundaries of the respective 9x9 sub-Sudoku always count.

Strategies for Solving

The basic techniques correspond to classic Sudoku. The difference is that certain entries in one sub-Sudoku can influence others. Shared cells and overlapping areas are especially important.

1. Check a single sub-Sudoku as a normal Sudoku

Start with a sub-Sudoku where many numbers are already filled. Often, simple certain entries can be found without viewing the entire multi Sudoku shape at once.

In the considered 9x9 sub-Sudoku, one row reads 43172689. The numbers 1, 2, 3, 4, 6, 7, 8, and 9 are already present. The only missing number is 5. Therefore, the last open cell in this row must be a 5.

This conclusion applies only to these nine cells of this specific sub-Sudoku row, not the entire visible width of the figure.

2. Hidden single candidate in a 3x3 block

Not every certain number arises from an almost complete row. Often, a number can only be in one position within a 3x3 block. In the following full Flower Sudoku grid, we identify the top-left 3x3 block of a sub-Sudoku and search for the number 5.

In this sub-Sudoku, the 5 is checked in the top-left 3x3 block. In the second and third rows, a 5 is already present, so it cannot be in those rows within this block. Also, the first and second columns of this sub-Sudoku already contain a 5. This excludes the first two cells in the first row of the block. Only the third cell in the first row remains. This cell must contain the 5.

This is a hidden single candidate. While not immediately obvious, for the number 5, only this one permitted position remains in the considered block.

3. Use a shared cell as a bridge

Shared cells are the most important feature of Flower Sudoku. A shared cell belongs to multiple sub-Sudokus. When a number is confidently determined there, it must be immediately considered in all involved sub-Sudokus.

In the leftmost row of the example, the sequence 123456.78 appears. Inside this sub-Sudoku, only the 9 is missing. The open cell also belongs to an adjacent sub-Sudoku. As soon as the 9 is entered, it also affects the 9s in that row.

The first entry is therefore not just a local progress but also a hint for the neighboring sub-Sudoku, because the same cell is part of a row, a column, and a 3x3 block there too.

4. Derive a next step from an overlap

In the neighboring sub-Sudoku, the relevant 9s row is 45697812. Only the 3 is missing. Therefore, this cell can also be confidently filled.

This example illustrates the typical multi Sudoku effect: first, a cell in one sub-Sudoku is confidently solved. Because this cell is shared, it immediately creates another certainty in the adjacent sub-Sudoku.

5. Carefully check candidates in overlaps

A normal Sudoku cell is restricted by a row, a column, and a 3x3 block. A shared cell can also belong to other rows, columns, or blocks of different sub-Sudokus. Therefore, a candidate in a shared cell must be allowed in all involved sub-Sudokus.

Practically, this means: do not check a shared cell only from the perspective of the sub-Sudoku you are working on. Intentionally switch to the other sub-Sudoku and verify the row, column, and block there as well. This often reveals shared cells earlier as definitive boundary or edge cells.

6. Clearly observe the boundaries of sub-Sudokus

Flower Sudoku appears as a large connected puzzle. Still, the logic derives from the individual 9x9 Sudokus. A visible row may contain parts of several sub-Sudoku rows. Always clearly identify which 9x9 Sudoku is currently being viewed during solving.

Typical solving sequence

1. Get an overview of the arrangement: a blossom-like layout of multiple 9x9 Sudokus with a strongly interconnected center.
2. Select a sub-Sudoku with many clues and look for confident traditional Sudoku steps.
3. Check almost complete rows, columns, and 3x3 blocks.
4. Search for hidden single candidates: numbers that can only be in one position in a particular area.
5. Mentally mark shared cells and overlapping areas.
6. Immediately transfer each confident entry in a shared cell to all involved sub-Sudokus.
7. Then check whether new candidates or eliminations arise in neighboring sub-Sudokus.
8. Regularly switch between sub-Sudokus instead of solving a region in isolation.
9. At each entry, verify its allowance in all related rows, columns, and 3x3 blocks.
10. End the puzzle only when all individual 9x9 Sudokus are fully and consistently solved.

Common mistakes

• Treat the entire figure as one large Sudoku. The rules apply within individual 9x9 Sudokus only.
• Update shared cells in only one sub-Sudoku. A shared cell affects all sub-Sudokus it belongs to.
• Misidentify boundaries. With offset grids, not every visible row is part of the same Sudoku row.
• Interpret empty areas as cells. Areas without grids are not filled.
• Rush into guesses too early. An incorrect entry can damage multiple sub-Sudokus at once.
• Fail to rigorously check candidates in overlaps. A candidate must be allowed in all involved rows, columns, and blocks.
• Fail to check after a certain confident entry. Shared cells often immediately lead to new eliminations.

Tips for beginners

• Start with a single sub-Sudoku and only solve secure steps there.
• Early on, identify shared areas where key connections form.
• Strictly observe the 9x9 boundaries of each Sudoku.
• Always check all involved sub-Sudokus for shared cells, not just the current region.
• Use candidate notes early, especially when multiple sub-Sudokus are involved.
• Switch perspectives: if progress stalls in one sub-Sudoku, verify neighboring shared cells.
• Ask yourself at each entry: in which sub-Sudoku is this number certain, and does it also influence another?
• View overlaps as additional clues, not just difficulties.

Flower Sudoku extends the classic Sudoku without changing its core logic. Every number continues to follow the known Sudoku rules. The challenge is to neatly link multiple sub-Sudokus. By consistently using shared cells, you can logically solve complex multi Sudoku shapes step by step.