@@ -79,14 +79,92 @@ private long mergeIntervals(List<int[]> active) {
 }
 
 
+/**
+* https://leetcode.com/problems/rectangle-area-ii/solution/
+*/
+public int rectangleArea2(int[][] rectangles) {
+int OPEN = 1, CLOSE = -1;
+int[][] events = new int[rectangles.length * 2][];
+Set<Integer> Xvals = new HashSet();
+int t = 0;
+for (int[] rec: rectangles) {
+events[t++] = new int[]{rec[1], OPEN, rec[0], rec[2]};
+events[t++] = new int[]{rec[3], CLOSE, rec[0], rec[2]};
+Xvals.add(rec[0]);
+Xvals.add(rec[2]);
+}
 
+Arrays.sort(events, (a, b) -> Integer.compare(a[0], b[0]));
 
+Integer[] X = Xvals.toArray(new Integer[0]);
+Arrays.sort(X);
+Map<Integer, Integer> Xi = new HashMap();
+for (int i = 0; i < X.length; ++i)
+Xi.put(X[i], i);
 
+Node active = new Node(0, X.length - 1, X);
+long ans = 0;
+long cur_x_sum = 0;
+int cur_y = events[0][0];
 
+for (int[] event: events) {
+int y = event[0], typ = event[1], x1 = event[2], x2 = event[3];
+ans += cur_x_sum * (y - cur_y);
+cur_x_sum = active.update(Xi.get(x1), Xi.get(x2), typ);
+cur_y = y;
 
-
+}
 
+ans %= 1_000_000_007;
+return (int) ans;
+}
 
 
+class Node {
+int start, end;
+Integer[] X;
+Node left, right;
+int count;
+long total;
+
+public Node(int start, int end, Integer[] X) {
+this.start = start;
+this.end = end;
+this.X = X;
+left = null;
+right = null;
+count = 0;
+total = 0;
+}
+
+public int getRangeMid() {
+return start + (end - start) / 2;
+}
+
+public Node getLeft() {
+if (left == null) left = new Node(start, getRangeMid(), X);
+return left;
+}
+
+public Node getRight() {
+if (right == null) right = new Node(getRangeMid(), end, X);
+return right;
+}
+
+public long update(int i, int j, int val) {
+if (i >= j) return 0;
+if (start == i && end == j) {
+count += val;
+} else {
+getLeft().update(i, Math.min(getRangeMid(), j), val);
+getRight().update(Math.max(getRangeMid(), i), j, val);
+}
+
+if (count > 0) total = X[end] - X[start];
+else total = getLeft().total + getRight().total;
+
+return total;
+}
+}
 
 }