Rules:
Fill the grid with digits 1 to N, so that each digit appears exactly once in each row or column.
Some cells should be shaded.
Clues with black circle indicate how many shaded skyscrapers are visible from that direction(non-shaded skyscrapers are ignored).
Some cells should be shaded.
Clues with black circle indicate how many shaded skyscrapers are visible from that direction(non-shaded skyscrapers are ignored).
Non-shaded clues indicate how many non-shaded skyscrapers are visible from that direction(shaded skyscrapers are ignored).
