Sum Skyscrapers Sudoku (188)

Place a number from 1-9 in each empty cell in the grid such that each row, column and marked 3×3 box contains each number exactly once. Each number represents the height of a building. The clues outside the grid indicate the sum of buildings visible from the corresponding direction. A taller building will hide any shorter buildings behind it.

Reference: WSC 2014 (42)