Heyawake

Heyawake is played on a rectangular grid of cells, divided into variously sized rectangular rooms. Some rooms may contain a single number. The object of the puzzle is to determine which cells should be painted black and which should be left blank.

The following rules are followed

1. Black cells may never be adjacent horizontally or vertically (diagonally is ok).
2. All white cells must be connected horizontally or vertically.
3. The number indicates exactly how many black cells there must be in that particular room.
4. A room which has no number may contain any number of black cells (including none).
5. Where a straight line of connected white cells is formed, it must not contain cells from more than two rooms..