题目：

题解：

class Solution:
    def getSkyline(self, buildings: List[List[int]]) -> List[List[int]]:
        buildings.sort(key=lambda bu:(bu[0],-bu[2],bu[1]))
        buildings.append([inf,inf,inf])
        heap = [[-inf,-inf,-inf]]
        ans = []
        for l,r,h in buildings:
            if heap[0][2] < l:
                topRight = heappop(heap)[2]
                while heap and topRight < l:
                    if heap[0][2] > topRight:
                        # 建筑群内有较较矮的建筑宽度比高的大，对齐进行切块
                        top = heappop(heap)
                        top[1], topRight = topRight, top[2]
                        # 如果新的切块也覆盖到新建筑，不需要再放入了
                        if topRight >= l: heappush(heap, top)
                        if ans[-1][1] != -top[0]: ans.append([top[1], -top[0]])
                    else: heappop(heap)
                if not heap: ans.append([topRight, 0])
            if not heap or h > -heap[0][0]: ans.append([l, h])
            if heap and heap[0][0] == -h and heap[0][2] < r: heap[0][2] = r
            else: heappush(heap, [-h,l,r])
        return ans[1:-1]