116 lines
4.2 KiB
Java
116 lines
4.2 KiB
Java
/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.spatialpartition;
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import java.util.ArrayList;
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import java.util.Enumeration;
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import java.util.Hashtable;
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/**
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* The quadtree data structure is being used to keep track of the objects' locations.
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* It has the insert(Point) and query(range) methods to insert a new object and find
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* the objects within a certain (rectangular) range respectively.
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*/
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public class QuadTree {
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Rect boundary;
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int capacity;
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boolean divided;
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Hashtable<Integer, Point> points;
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QuadTree northwest;
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QuadTree northeast;
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QuadTree southwest;
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QuadTree southeast;
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QuadTree(Rect boundary, int capacity) {
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this.boundary = boundary;
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this.capacity = capacity;
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this.divided = false;
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this.points = new Hashtable<Integer, Point>();
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this.northwest = null;
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this.northeast = null;
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this.southwest = null;
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this.southeast = null;
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}
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void insert(Point p) {
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if (!this.boundary.contains(p)) {
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return;
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} else {
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if (this.points.size() < this.capacity) {
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points.put(p.id, p);
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} else {
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if (!this.divided) {
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this.divide();
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}
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if (this.northwest.boundary.contains(p)) {
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this.northwest.insert(p);
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} else if (this.northeast.boundary.contains(p)) {
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this.northeast.insert(p);
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} else if (this.southwest.boundary.contains(p)) {
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this.southwest.insert(p);
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} else if (this.southeast.boundary.contains(p)) {
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this.southeast.insert(p);
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}
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}
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}
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}
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void divide() {
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Rect nw = new Rect(this.boundary.x - this.boundary.width / 4, this.boundary.y + this.boundary.height / 4,
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this.boundary.width / 2, this.boundary.height / 2);
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this.northwest = new QuadTree(nw , this.capacity);
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Rect ne = new Rect(this.boundary.x + this.boundary.width / 4, this.boundary.y + this.boundary.height / 4,
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this.boundary.width / 2, this.boundary.height / 2);
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this.northeast = new QuadTree(ne , this.capacity);
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Rect sw = new Rect(this.boundary.x - this.boundary.width / 4, this.boundary.y - this.boundary.height / 4,
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this.boundary.width / 2, this.boundary.height / 2);
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this.southwest = new QuadTree(sw , this.capacity);
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Rect se = new Rect(this.boundary.x + this.boundary.width / 4, this.boundary.y - this.boundary.height / 4,
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this.boundary.width / 2, this.boundary.height / 2);
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this.southeast = new QuadTree(se , this.capacity);
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this.divided = true;
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}
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ArrayList<Point> query(Rect r, ArrayList<Point> relevantPoints) {
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//could also be a circle instead of a rectangle
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if (this.boundary.intersects(r)) {
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for (Enumeration<Integer> e = this.points.keys(); e.hasMoreElements();) {
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Integer i = e.nextElement();
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if (r.contains(this.points.get(i))) {
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relevantPoints.add(this.points.get(i));
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}
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}
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if (this.divided) {
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this.northwest.query(r, relevantPoints);
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this.northeast.query(r, relevantPoints);
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this.southwest.query(r, relevantPoints);
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this.southeast.query(r, relevantPoints);
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}
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}
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return relevantPoints;
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}
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}
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