7 – doku Rules
Place numbers in the grid. When completed the grid will have the following properties:
- Contains 28 numbers. One 1, two 2’s, … seven 7’s. This will leave 21 empty cells.
- Each row contains exactly four numbers, and those numbers sum to 20.
- Each column contains exactly four numbers, and those numbers sum to 20.
- Cells containing numbers form a single edge-connected region (i.e. a chess rook could traverse all cells with numbers without entering or crossing an empty cell).
- No 2x2 block contains four numbers (i.e. there must be at least one empty cell in every 2x2 block).
- Blue numbers outside the grid match the value of the nearest filled cell in that row or column. This is not necessarily the nearest cell as there can be empty cells in between.
Examples
Example 1: Puzzle and solution.
Example 2: An almost solution to the puzzle above. This satisfies all the rules except for the fourth bullet point. The cells with numbers do not form a single edge-connected region (i.e. any rook move that starts in the blue region and ends in the red region must traverse at least one empty cell).
Example 3: An almost solution to the puzzle from the first example. This satisfies all the rules except for the fifth bullet point. There is a 2x2 sub-grid that contains four numbers.
