天际线问题

Posted 2022-02-09 Alice_yufeng

class Solution 
    public List<List<Integer>> getSkyline(int[][] buildings) 
        PriorityQueue<int[]> pq = new PriorityQueue<int[]>((a, b) -> b[1] - a[1]);
        List<Integer> boundaries = new ArrayList<Integer>();
        for (int[] building : buildings) 
            boundaries.add(building[0]);
            boundaries.add(building[1]);
        
        Collections.sort(boundaries);

        List<List<Integer>> ret = new ArrayList<List<Integer>>();
        int n = buildings.length, idx = 0;
        for (int boundary : boundaries) 
            while (idx < n && buildings[idx][0] <= boundary) 
                pq.offer(new int[]buildings[idx][1], buildings[idx][2]);
                idx++;
            
            while (!pq.isEmpty() && pq.peek()[0] <= boundary) 
                pq.poll();
            

            int maxn = pq.isEmpty() ? 0 : pq.peek()[1];
            if (ret.size() == 0 || maxn != ret.get(ret.size() - 1).get(1)) 
                ret.add(Arrays.asList(boundary, maxn));
            
        
        return ret;