Find any point that is covered by most rectangles

http://www.cnblogs.com/Gryffin/p/7468676.html
Given an array of rectangles consisting of left top and right down points [[x1,y1, x2, y2],[x3,y3,x4,y4],...] , find any point that is covered by most rectangles.

    public static class Rectangle {
        int x1;
        int y1;
        int x2;
        int y2;
        Rectangle(int x1, int y1, int x2, int y2) {
            this.x1 = x1;
            this.x2 = x2;
            this.y1 = y1;
            this.y2 = y2;
        }
        @Override
        public String toString() {
            return x1 + "|" + y1 + "|" + x2 + "|" + y2;
        }
    }
    public int[] getArea(List<Rectangle> rects) {
        Set<Integer> ys = new HashSet<Integer>();
        Map<Integer, List<Rectangle>> map = new HashMap<Integer, List<Rectangle>>();
        for (Rectangle rect : rects) {
            ys.add(rect.y1);
            ys.add(rect.y2);
            List<Rectangle> list = map.getOrDefault(rect.y1, new ArrayList<>());
            list.add(rect);
            map.put(rect.y1, list);
            list = map.getOrDefault(rect.y2, new ArrayList<>());
            list.add(rect);
            map.put(rect.y2, list);
        }
        List<Integer> yList = new ArrayList<Integer>(ys);
        Collections.sort(yList);
        PriorityQueue<Rectangle> pq = new PriorityQueue<Rectangle>((o1, o2) -> Integer.compare(o1.y2, o2.y2));
        int ans = 0;
        int ans_x = 0;
        int ans_y = 0;
        for (int y : yList) {
            List<Rectangle> list = map.get(y);
            if (list == null) {
                continue;
            }
            for (Rectangle rect : list) {
                if (rect.y1 == y) {
                    pq.add(rect);
                }
            }
            int[] starts = new int[pq.size()];
            int[] ends = new int[pq.size()];
            int counter = 0;
            System.out.println(pq.toString());
            for (Rectangle rect : pq) {
                starts[counter] = rect.x1;
                ends[counter++] = rect.x2;
            }
            Arrays.sort(starts);
            Arrays.sort(ends);
            int r = 0;
            int index = 0;
            int pos = 0;
            for (int i = 0; i < starts.length; i++) {
                if (starts[i] < ends[index]) {
                    r++;
                    pos = ends[index];
                } else {
                    index++;
                }
            }
            if (r > ans) {
                ans = r;
                ans_x = pos;
                ans_y = y;
            }
            while (!pq.isEmpty() && pq.peek().y2 <= y) {
                pq.poll();
            }
        }
        return new int[] {ans_x, ans_y, ans};
    }

Given an array of rectangles consisting of left top and right down points
[[x1,y1, x2, y2],[x3,y3,x4,y4],...] , find the area covered by all these rectangles.

    public static class Rectangle {
        int x1;
        int y1;
        int x2;
        int y2;
        Rectangle(int x1, int y1, int x2, int y2) {
            this.x1 = x1;
            this.x2 = x2;
            this.y1 = y1;
            this.y2 = y2;
        }
        @Override
        public String toString() {
            return x1 + "|" + y1 + "|" + x2 + "|" + y2;
        }
    }
    public int getArea2(List<Rectangle> rects) {
        int ans = 0;
        Set<Integer> ys = new HashSet<Integer>();
        Map<Integer, List<Rectangle>> map = new HashMap<Integer, List<Rectangle>>();
        for (Rectangle rect : rects) {
            ys.add(rect.y1);
            ys.add(rect.y2);
            List<Rectangle> list = map.getOrDefault(rect.y1, new ArrayList<>());
            list.add(rect);
            map.put(rect.y1, list);
            list = map.getOrDefault(rect.y2, new ArrayList<>());
            list.add(rect);
            map.put(rect.y2, list);
        }
        System.out.println(map.toString());
        List<Integer> yList = new ArrayList<Integer>(ys);
        Collections.sort(yList);
        System.out.println(yList.toString());
        PriorityQueue<Rectangle> pq = new PriorityQueue<Rectangle>((o1, o2) -> Integer.compare(o1.y2, o2.y2));
        for (int i = 0; i < yList.size(); i++) {
            int y = yList.get(i);
            List<Rectangle> list = map.get(y);
            if (list == null) {
                continue;
            }
            System.out.println(pq.toString());
            if (!pq.isEmpty()) {
                int[] starts = new int[pq.size()];
                int[] ends = new int[pq.size()];
                int counter = 0;
                int deltaY = yList.get(i) - yList.get(i - 1);

                for (Rectangle rect : pq) {
                    starts[counter] = rect.x1;
                    ends[counter++] = rect.x2;
                }
                Arrays.sort(starts);
                Arrays.sort(ends);
                int a = 0;
                int b = 0;
                int r = 0;
                while (a < starts.length) {
                    if (starts[a] < ends[b]) {
                        if (r == 0) {
                            ans += (ends[b] - starts[a]) * deltaY;
                            System.out.println("ans: " + ans);
                        }
                        a++;
                        r++;
                    } else {
                        r--;
                        b++;
                    }
                }
                while (!pq.isEmpty() && pq.peek().y2 == y) {
                    pq.poll();
                }
            }


            for (Rectangle rect : list) {
                if (rect.y1 == y) {
                    pq.add(rect);
                }
            }
        }
        return ans;
    }