Given buildings, return the skyline formed by these buildings.
Sample Input:
[[2,9,10],[3,7,15],[5,12,12],[15,20,10],[19,24,8]]
Sample Output:
[[2,10],[3,15],[7,12],[12,0],[15,10],[20,8],[24,0]]
Hints
Hint 1
Use sweep line algorithm
Hint 2
Sort critical points (start and end of buildings)
Hint 3
Use max-heap to track current max height
