Leetcode Problem 391 Perfect Rectangle

Author: jayanthreddy1997

leetcode/java/sets/PerfectRectangle391.java

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+class PerfectRectangle391 {
+    public boolean isRectangleCover(int[][] rectangles) {
+        if(rectangles==null || rectangles.length==0 || rectangles[0].length==0)
+            return false;
+        int N = rectangles.length;
+
+        // Identify Overlaps - TreeSet with custom comparator: O(n*log(n))
+        // Sum of areas equal to covering area : O(n)
+        // Overall solution : O(n*log(n))
+
+        Set<int[]> set = new TreeSet<>((int[] a, int[] b) -> {
+            if (a[3] <= b[1]) {
+                return -1;
+            } else if (a[1] >= b[3]) {
+                return 1;
+            } else if (a[2] <= b[0]) {
+                return -1;
+            } else if (a[0] >= b[2]) {
+                return 1;
+            } else return 0;
+        });
+
+        int[] coverBottomLeft = {rectangles[0][0], rectangles[0][1]};
+        int[] coverTopRight = {rectangles[0][2], rectangles[0][3]};
+
+        long totalArea = 0;
+        for (int i=0; i<N; i++) {
+            if(!set.add(rectangles[i]))
+                return false;
+
+            totalArea += ((long)(rectangles[i][3] - rectangles[i][1])) * ((long)(rectangles[i][2] - rectangles[i][0]));
+            coverBottomLeft[0] = Math.min(coverBottomLeft[0], rectangles[i][0]);
+            coverBottomLeft[1] = Math.min(coverBottomLeft[1], rectangles[i][1]);
+            coverTopRight[0] = Math.max(coverTopRight[0], rectangles[i][2]);
+            coverTopRight[1] = Math.max(coverTopRight[1], rectangles[i][3]);
+        }
+        long coverArea = ((long)(coverTopRight[0] - coverBottomLeft[0])) * ((long)(coverTopRight[1] - coverBottomLeft[1]));
+
+        return (totalArea == coverArea);
+    }
+}