Compute city skyline outline

You are given a list of rectangular buildings in a 2D city skyline. Each building is represented by three integers `[L, R, H]`: - `L`: the x-coordinate of the left edge of the building, - `R`: the x-coordinate of the right edge of the building (`L < R`), - `H`: the height of the building. All buildings stand on a flat horizontal line (y = 0) and extend vertically up to height `H`. Buildings may overlap in the x-dimension. Your task is to compute the *skyline* formed by these buildings, as seen from a distance. The skyline should be represented as a list of **key points** `[x, height]` that describe the outer contour of the union of all buildings. A **key point** is a point where the height of the skyline changes. The output list must satisfy all of the following: 1. The list is sorted by increasing `x`. 2. No two consecutive points have the same height (i.e., the height must change at each key point). 3. The first point has a height greater than 0. 4. The last point has height 0, marking the end of the skyline. ### Input - An integer `n` — the number of buildings. - A list of `n` buildings, where each building is given as a triple `[L, R, H]` of integers. You may assume: - `1 <= n <= 10^4` - `0 <= L < R <= 10^9` - `1 <= H <= 10^9` ### Output Return a list of key points representing the skyline. Each key point is a pair `[x, height]` (or a 2-element array/tuple) of integers. ### Example Input: - `n = 3` - buildings = `[[2, 9, 10], [3, 7, 15], [5, 12, 12]]` One valid output: - `[[2, 10], [3, 15], [7, 12], [12, 0]]` Explanation (informal): - From x = 2 to 3, the highest building has height 10. - From x = 3 to 7, the highest building has height 15. - From x = 7 to 12, the remaining highest building has height 12. - After x = 12, there are no buildings, so the height drops to 0. Design an algorithm to compute the skyline key points for the given buildings.