Skyline Problem Solution

class Solution:
    def getSkyline(self, buildings):
        """
        :type buildings: List[List[int]]
        :rtype: List[List[int]]
        """
        vectors = {}
        for li, ri, hi in buildings:
            vectors[li] = ([], [])
            vectors[ri] = ([], [])

        for li, ri, hi in buildings:
            vectors[li][0].append(hi)
            vectors[ri][1].append(hi)

        fringe = [0]
        skyline = []
        last_height = 0
        for x, (ups, downs) in sorted(vectors.items()):
            fringe.extend(ups)
            for e in downs:
                fringe.remove(e)

            height = max(fringe)
            if height != last_height:
                skyline.append((x, height))
                last_height = height
        return skyline