Update SkylineAlgorithm.java

divideconquer/SkylineAlgorithm.java

@@ -1,19 +1,15 @@
-package skylinealgorithm;
-
 import java.util.ArrayList;
 import java.util.Comparator;
 
 /**
- *
  * @author dimgrichr
- * 
+ * <p>
  * Space complexity: O(n)
  * Time complexity: O(nlogn), because it is a divide and conquer algorithm
  */
 public class SkylineAlgorithm {
     private ArrayList<Point> points;
 
-    
     /**
      * Main constructor of the application.
      * ArrayList points gets created, which represents the sum of all edges.
@@ -42,6 +38,7 @@ public class SkylineAlgorithm {
      * with arguments the corresponding half of the initial ArrayList each time.
      * Once the flashback has ended, the function produceFinalSkyLine gets called,
      * in order to produce the final skyline, and return it.
+     *
      * @param list, the initial list of points
      * @return leftSkyLine, the combination of first half's and second half's skyline
      * @see Point
@@ -53,12 +50,10 @@ public class SkylineAlgorithm {
         int size = list.size();
         if (size == 1) {
             return list;
-        }
+        } else if (size == 2) {
-        else if(size==2){
             if (list.get(0).dominates(list.get(1))) {
                 list.remove(1);
-            }
+            } else {
-            else{
                 if (list.get(1).dominates(list.get(0))) {
                     list.remove(0);
                 }
@@ -72,15 +67,12 @@ public class SkylineAlgorithm {
         for (int i = 0; i < list.size(); i++) {
             if (i < list.size() / 2) {
                 leftHalf.add(list.get(i));
-            }
+            } else {
-            else{
                 rightHalf.add(list.get(i));
             }
         }
-        ArrayList<Point> leftSubSkyLine=new ArrayList<>();
+        ArrayList<Point> leftSubSkyLine = produceSubSkyLines(leftHalf);
-        ArrayList<Point> rightSubSkyLine=new ArrayList<>();
+        ArrayList<Point> rightSubSkyLine= produceSubSkyLines(rightHalf);
-        leftSubSkyLine=produceSubSkyLines(leftHalf);
-        rightSubSkyLine=produceSubSkyLines(rightHalf);
 
         // skyline is produced
         return produceFinalSkyLine(leftSubSkyLine, rightSubSkyLine);
@@ -97,6 +89,7 @@ public class SkylineAlgorithm {
      * are dominated, so they are not part of the final skyline.
      * Finally, the "cleaned" first half's and second half's skylines, are combined,
      * producing the final skyline, which is returned.
+     *
      * @param left  the skyline of the left part of points
      * @param right the skyline of the right part of points
      * @return left the final skyline
@@ -136,12 +129,13 @@ public class SkylineAlgorithm {
     }
 
 
-
     public static class Point {
         private int x;
         private int y;
+
         /**
          * The main constructor of Point Class, used to represent the 2 Dimension points.
+         *
          * @param x the point's x-value.
          * @param y the point's y-value.
          */
@@ -149,34 +143,35 @@ public class SkylineAlgorithm {
             this.x = x;
             this.y = y;
         }
+
         /**
          * @return x, the x-value
          */
         public int getX() {
             return x;
         }
+
         /**
          * @return y, the y-value
          */
         public int getY() {
             return y;
         }
+
         /**
          * Based on the skyline theory,
          * it checks if the point that calls the function dominates the argument point.
+         *
          * @param p1 the point that is compared
          * @return true if the point wich calls the function dominates p1
          * false otherwise.
          */
         public boolean dominates(Point p1) {
-            
             // checks if p1 is dominated
-            if((this.x<p1.x && this.y<=p1.y) || (this.x<=p1.x && this.y<p1.y)){
+            return (this.x < p1.x && this.y <= p1.y) || (this.x <= p1.x && this.y < p1.y);
-                return true;
-            }
-            return false;
         }
     }
+
     /**
      * It is used to compare the 2 Dimension points,
      * based on their x-values, in order get sorted later.
@@ -184,7 +179,7 @@ public class SkylineAlgorithm {
     class XComparator implements Comparator<Point> {
         @Override
         public int compare(Point a, Point b) {
-        return a.x < b.x ? -1 : a.x == b.x ? 0 : 1;
+            return Integer.compare(a.x, b.x);
         }
     }
 }