public List<List<Integer>> getSkyline(int[][] buildings) {

List<List<Integer>> result = new ArrayList<>();

List<int[]> heights = new ArrayList<>();

for (int[] building : buildings) {

heights.add(new int[]{building[0], -1 * building[2]});

heights.add(new int[]{building[1], 1 * building[2]});

}

Collections.sort(heights, (a, b) -> a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]);

PriorityQueue<Integer> pq = new PriorityQueue<>((a, b) -> b - a);

pq.add(0);

int previousMax = 0;

for (int[] height : heights) {

if (height[1] < 0) {

pq.add(-1 * height[1]);

} else {

pq.remove(height[1]);

}

int currentMax = pq.peek();

if (currentMax != previousMax) {

result.add(Arrays.asList(height[0], currentMax));

previousMax = currentMax;

}

}

return result;

}