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Coral (Overlapping) (378)
Other names: Double coral
Instruction:
Put a circle or a cross into every empty cell such that all cells with a circle are connected orthogonally into a single region, and all cells with a cross are connected orthogonally into a single region. All cells that do not have a circle must be connected orthogonally (through other cells that do not have a circle) to the edge of the grid. All cells that do not have a cross must be connected orthogonally (through other cells that do not have a cross) to the edge of the grid. No 2×2 group of cells may have circles in all four cells. No 2×2 group of cells may have crosses in all four cells.
Some cells contain both a circle and a cross; all such cells are given to you.
The numbers to the left of the main grid represent the lengths of contiguous cell blocks with crosses in the corresponding row. The numbers above the main grid represent the lengths of contiguous cell blocks with circles in the corresponding column. The lengths are not necessarily given in order from left to right (or top to bottom), and cell blocks must contain at least one cell without the relevant symbol between them. As a special case, if the single clue “0” is given, it means there should be no cells of the relevant symbol in that row (or column).
It is possible that not all rows and columns have given numbers. It is up to you to determine which symbols go in which cells without that information.