diff --git a/divideconquer/SkylineAlgorithm.java b/divideconquer/SkylineAlgorithm.java
index f1b1f44c..51bce90c 100644
--- a/divideconquer/SkylineAlgorithm.java
+++ b/divideconquer/SkylineAlgorithm.java
@@ -1,36 +1,32 @@
-package skylinealgorithm;
-
import java.util.ArrayList;
import java.util.Comparator;
/**
- *
* @author dimgrichr
- *
+ *
* Space complexity: O(n)
* Time complexity: O(nlogn), because it is a divide and conquer algorithm
*/
public class SkylineAlgorithm {
private ArrayList points;
-
-
+
/**
* Main constructor of the application.
* ArrayList points gets created, which represents the sum of all edges.
*/
- public SkylineAlgorithm(){
+ public SkylineAlgorithm() {
points = new ArrayList<>();
}
-
-
+
+
/**
* @return points, the ArrayList that includes all points.
*/
- public ArrayList getPoints(){
+ public ArrayList getPoints() {
return points;
}
-
-
+
+
/**
* The main divide and conquer, and also recursive algorithm.
* It gets an ArrayList full of points as an argument.
@@ -38,55 +34,51 @@ public class SkylineAlgorithm {
* the ArrayList is returned as it is, or with one less point
* (if the initial size is 2 and one of it's points, is dominated by the other one).
* On the other hand, if the ArrayList's size is bigger than 2,
- * the function is called again, twice,
+ * the function is called again, twice,
* 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
* @see produceFinalSkyLine
*/
- public ArrayList produceSubSkyLines(ArrayList list){
-
- //part where function exits flashback
+ public ArrayList produceSubSkyLines(ArrayList list) {
+
+ // part where function exits flashback
int size = list.size();
- if(size == 1){
+ if (size == 1) {
return list;
- }
- else if(size==2){
- if(list.get(0).dominates(list.get(1))){
+ } else if (size == 2) {
+ if (list.get(0).dominates(list.get(1))) {
list.remove(1);
- }
- else{
- if(list.get(1).dominates(list.get(0))){
+ } else {
+ if (list.get(1).dominates(list.get(0))) {
list.remove(0);
}
}
return list;
}
-
- //recursive part of the function
- ArrayList leftHalf=new ArrayList<>();
- ArrayList rightHalf=new ArrayList<>();
- for (int i=0;i leftHalf = new ArrayList<>();
+ ArrayList rightHalf = new ArrayList<>();
+ 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 leftSubSkyLine=new ArrayList<>();
- ArrayList rightSubSkyLine=new ArrayList<>();
- leftSubSkyLine=produceSubSkyLines(leftHalf);
- rightSubSkyLine=produceSubSkyLines(rightHalf);
-
- //skyline is produced
- return produceFinalSkyLine(leftSubSkyLine,rightSubSkyLine);
+ ArrayList leftSubSkyLine = produceSubSkyLines(leftHalf);
+ ArrayList rightSubSkyLine= produceSubSkyLines(rightHalf);
+
+ // skyline is produced
+ return produceFinalSkyLine(leftSubSkyLine, rightSubSkyLine);
}
-
-
+
+
/**
* The first half's skyline gets cleared
* from some points that are not part of the final skyline
@@ -97,94 +89,97 @@ 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 left the skyline of the left part of points
* @param right the skyline of the right part of points
* @return left the final skyline
*/
- public ArrayList produceFinalSkyLine(ArrayList left, ArrayList right){
-
- //dominated points of ArrayList left are removed
- for(int i=0;ileft.get(i+1).y){
+ public ArrayList produceFinalSkyLine(ArrayList left, ArrayList right) {
+
+ // dominated points of ArrayList left are removed
+ for (int i = 0; i < left.size() - 1; i++) {
+ if (left.get(i).x == left.get(i + 1).x && left.get(i).y > left.get(i + 1).y) {
left.remove(i);
i--;
}
}
-
- //minimum y-value is found
- int min=left.get(0).y;
- for(int i=1;ileft.get(i).y){
+
+ // minimum y-value is found
+ int min = left.get(0).y;
+ for (int i = 1; i < left.size(); i++) {
+ if (min > left.get(i).y) {
min = left.get(i).y;
- if(min==1){
- i=left.size();
+ if (min == 1) {
+ i = left.size();
}
}
}
-
- //dominated points of ArrayList right are removed
- for(int i=0;i=min){
+
+ // dominated points of ArrayList right are removed
+ for (int i = 0; i < right.size(); i++) {
+ if (right.get(i).y >= min) {
right.remove(i);
i--;
}
}
-
- //final skyline found and returned
+
+ // final skyline found and returned
left.addAll(right);
return left;
}
-
-
- public static class Point{
+
+ 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.
*/
- public Point(int x, int y){
- this.x=x;
- this.y=y;
+ public Point(int x, int y) {
+ this.x = x;
+ this.y = y;
}
+
/**
* @return x, the x-value
*/
- public int getX(){
+ public int getX() {
return x;
}
+
/**
* @return y, the y-value
*/
- public int getY(){
+ 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.
+ * false otherwise.
*/
- public boolean dominates(Point p1){
-
- //checks if p1 is dominated
- if((this.x {
- @Override
- public int compare(Point a, Point b) {
- return a.x < b.x ? -1 : a.x == b.x ? 0 : 1;
- }
+ @Override
+ public int compare(Point a, Point b) {
+ return Integer.compare(a.x, b.x);
+ }
}
}