Skyscrapers

Skyscrapers (Skyline) is a Sudoku-like logic puzzle. You have to enter a number into each cell of the grid so that a given number of numbers are visible from the outside.

Rules: In some cells of the grid, you have to enter numbers from the specified range of 1–N. Each number appears exactly once in each row and column. Some cells may be left blank.
A number at the edge of the grid indicates how many numbers are higher than all previous numbers if you “look into” the grid at the given position.