Skyscrapers (diagonal) (938)

Place a number from 1 to X (integers only) into each cell so that each number appears exactly once in each row and column. (X is the number of cells in each row.) Each number represents a skyscraper of its respective height.
The numbers outside the grid indicate how many skyscrapers can be seen in the respective diagonal from the respective direction; smaller skyscrapers are hidden behind higher ones. Skyscrapers of the same height hide each other.

Reference: WPF (1)