Spatial partition pattern #562 (#828)

* Spatial partition * Update pom.xml * Update Bubble.java - pmd * Update Rect.java - pmd
2026-05-14 16:58:47 +00:00 · 2018-12-23 03:07:31 +05:30
parent 7b8c9b07ed
commit a6749cb63e
14 changed files with 914 additions and 0 deletions
@@ -0,0 +1,115 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.spatialpartition;
+
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.Hashtable;
+
+/**
+ * The quadtree data structure is being used to keep track of the objects' locations.
+ * It has the insert(Point) and query(range) methods to insert a new object and find
+ * the objects within a certain (rectangular) range respectively.
+ */
+
+public class QuadTree {
+  Rect boundary;
+  int capacity;
+  boolean divided;
+  Hashtable<Integer, Point> points;
+  QuadTree northwest;
+  QuadTree northeast;
+  QuadTree southwest;
+  QuadTree southeast;
+
+  QuadTree(Rect boundary, int capacity) {
+    this.boundary = boundary;
+    this.capacity = capacity;
+    this.divided = false;
+    this.points = new Hashtable<Integer, Point>();
+    this.northwest = null; 
+    this.northeast = null; 
+    this.southwest = null; 
+    this.southeast = null;
+  }
+
+  void insert(Point p) {
+    if (!this.boundary.contains(p)) {
+      return;
+    } else {
+      if (this.points.size() < this.capacity) {
+        points.put(p.id, p);
+      } else {
+        if (!this.divided) {
+          this.divide();
+        }
+
+        if (this.northwest.boundary.contains(p)) {
+          this.northwest.insert(p);
+        } else if (this.northeast.boundary.contains(p)) {
+          this.northeast.insert(p);
+        } else if (this.southwest.boundary.contains(p)) {
+          this.southwest.insert(p);
+        } else if (this.southeast.boundary.contains(p)) {
+          this.southeast.insert(p);
+        }
+      }
+    }
+  }
+
+  void divide() {
+    Rect nw = new Rect(this.boundary.x - this.boundary.width / 4, this.boundary.y + this.boundary.height / 4, 
+          this.boundary.width / 2, this.boundary.height / 2);
+    this.northwest = new QuadTree(nw , this.capacity);
+    Rect ne = new Rect(this.boundary.x + this.boundary.width / 4, this.boundary.y + this.boundary.height / 4, 
+          this.boundary.width / 2, this.boundary.height / 2);
+    this.northeast = new QuadTree(ne , this.capacity);
+    Rect sw = new Rect(this.boundary.x - this.boundary.width / 4, this.boundary.y - this.boundary.height / 4, 
+          this.boundary.width / 2, this.boundary.height / 2);
+    this.southwest = new QuadTree(sw , this.capacity);
+    Rect se = new Rect(this.boundary.x + this.boundary.width / 4, this.boundary.y - this.boundary.height / 4, 
+          this.boundary.width / 2, this.boundary.height / 2);
+    this.southeast = new QuadTree(se , this.capacity);
+    this.divided = true;
+  }
+
+  ArrayList<Point> query(Rect r, ArrayList<Point> relevantPoints) {
+    //could also be a circle instead of a rectangle
+    if (this.boundary.intersects(r)) {
+      for (Enumeration<Integer> e = this.points.keys(); e.hasMoreElements();) {
+        Integer i = e.nextElement();
+        if (r.contains(this.points.get(i))) {
+          relevantPoints.add(this.points.get(i));
+        }
+      }
+      if (this.divided) {
+        this.northwest.query(r, relevantPoints);
+        this.northeast.query(r, relevantPoints);
+        this.southwest.query(r, relevantPoints);
+        this.southeast.query(r, relevantPoints);
+      }
+    }
+    return relevantPoints;
+  }
+}