[BAEL-3485] - Java Range lookup problem

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/Point.java

@@ -0,0 +1,24 @@
+package com.baeldung.algorithms.quadtree;
+
+public class Point {
+    private float x;
+    private float y;
+
+    public Point(float x, float y) {
+        this.x = x;
+        this.y = y;
+    }
+
+    public float getX() {
+        return x;
+    }
+
+    public float getY() {
+        return y;
+    }
+
+    @Override
+    public String toString() {
+        return "[" + x + " , " + y + "]";
+    }
+}

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/QuadTree.java

@@ -0,0 +1,109 @@
+package com.baeldung.algorithms.quadtree;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class QuadTree {
+    private static final int MAX_POINTS = 3;
+    private Region area;
+    private List<Point> points = new ArrayList<>();
+    private List<QuadTree> quadTrees = new ArrayList<>();
+    private StringBuilder searchTraversePath;
+
+    public QuadTree(Region area) {
+        this.area = area;
+    }
+
+    public boolean addPoint(Point point) {
+        if (this.area.containsPoint(point)) {
+            if (this.points.size() < MAX_POINTS) {
+                this.points.add(point);
+                return true;
+            } else {
+                if (this.quadTrees.size() == 0) {
+                    createQuadrants();
+                }
+                return addPointToOneQuadrant(point);
+            }
+        }
+        return false;
+    }
+
+    private boolean addPointToOneQuadrant(Point point) {
+        boolean isPointAdded;
+        for (int i = 0; i < 4; i++) {
+            isPointAdded = this.quadTrees.get(i)
+                .addPoint(point);
+            if (isPointAdded)
+                return true;
+        }
+        return false;
+    }
+
+    private void createQuadrants() {
+        Region region;
+        for (int i = 0; i < 4; i++) {
+            region = this.area.getQuadrant(i);
+            quadTrees.add(new QuadTree(region));
+        }
+    }
+
+    public List<Point> search(Region searchRegion, List<Point> matches, String depthIndicator) {
+        searchTraversePath = new StringBuilder();
+        if (matches == null) {
+            matches = new ArrayList<Point>();
+            searchTraversePath.append(depthIndicator)
+                .append("Search Boundary =")
+                .append(searchRegion)
+                .append("\n");
+        }
+        if (!this.area.doesOverlap(searchRegion)) {
+            return matches;
+        } else {
+            for (Point point : points) {
+                if (searchRegion.containsPoint(point)) {
+                    searchTraversePath.append(depthIndicator)
+                    .append("Found match " + point)
+                    .append("\n");
+                    matches.add(point);
+                }
+            }
+            if (this.quadTrees.size() > 0) {
+                for (int i = 0; i < 4; i++) {
+                    searchTraversePath.append(depthIndicator)
+                        .append("Q")
+                        .append(i)
+                        .append("-->")
+                        .append(quadTrees.get(i).area)
+                        .append("\n");
+                    quadTrees.get(i)
+                        .search(searchRegion, matches, depthIndicator + "\t");
+                    this.searchTraversePath.append(quadTrees.get(i)
+                        .printSearchTraversePath());
+                }
+            }
+        }
+        return matches;
+    }
+
+    public String printTree(String depthIndicator) {
+        String str = "";
+        if (depthIndicator == "") {
+            str += "Root-->" + area.toString() + "\n";
+        }
+
+        for (Point point : points) {
+            str += depthIndicator + point.toString() + "\n";
+        }
+        for (int i = 0; i < quadTrees.size(); i++) {
+            str += depthIndicator + "Q" + String.valueOf(i) + "-->" + quadTrees.get(i).area.toString() + "\n";
+            str += quadTrees.get(i)
+                .printTree(depthIndicator + "\t");
+        }
+        return str;
+    }
+
+    public String printSearchTraversePath() {
+        return searchTraversePath.toString();
+    }
+}

algorithms-searching/src/main/java/com/baeldung/algorithms/quadtree/Region.java

@@ -0,0 +1,85 @@
+package com.baeldung.algorithms.quadtree;
+
+public class Region {
+    private float x1;
+    private float y1;
+    private float x2;
+    private float y2;
+
+    public Region(float x1, float y1, float x2, float y2) {
+        if (x1 >= x2 || y1 >= y2)
+            throw new IllegalArgumentException("(x1,y1) should be lesser than (x2,y2)");
+        this.x1 = x1;
+        this.y1 = y1;
+        this.x2 = x2;
+        this.y2 = y2;
+    }
+
+    public Region getQuadrant(int quadrantIndex) {
+        float quadrantWidth = (this.x2 - this.x1) / 2;
+        float quadrantHeight = (this.y2 - this.y1) / 2;
+
+        // 0=SW, 1=NW, 2=NE, 3=SE
+        switch (quadrantIndex) {
+        case 0:
+            return new Region(x1, y1, x1 + quadrantWidth, y1 + quadrantHeight);
+        case 1:
+            return new Region(x1, y1 + quadrantHeight, x1 + quadrantWidth, y2);
+        case 2:
+            return new Region(x1 + quadrantWidth, y1 + quadrantHeight, x2, y2);
+        case 3:
+            return new Region(x1 + quadrantWidth, y1, x2, y1 + quadrantHeight);
+        }
+        return null;
+    }
+
+    public boolean containsPoint(Point point) {
+        // Consider left and top side to be inclusive for points on border
+        return point.getX() >= this.x1 
+            && point.getX() < this.x2 
+            && point.getY() >= this.y1 
+            && point.getY() < this.y2;
+    }
+
+    public boolean doesOverlap(Region testRegion) {
+        // Is test region completely to left of my region?
+        if (testRegion.getX2() < this.getX1()) {
+            return false;
+        }
+        // Is test region completely to right of my region?
+        if (testRegion.getX1() > this.getX2()) {
+            return false;
+        }
+        // Is test region completely above my region?
+        if (testRegion.getY1() > this.getY2()) {
+            return false;
+        }
+        // Is test region completely below my region?
+        if (testRegion.getY2() < this.getY1()) {
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        return "[Region (x1=" + x1 + ", y1=" + y1 + "), (x2=" + x2 + ", y2=" + y2 + ")]";
+    }
+
+    public float getX1() {
+        return x1;
+    }
+
+    public float getY1() {
+        return y1;
+    }
+
+    public float getX2() {
+        return x2;
+    }
+
+    public float getY2() {
+        return y2;
+    }
+
+}

algorithms-searching/src/test/java/com/baeldung/algorithms/quadtree/QuadTreeSearchTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.algorithms.quadtree;
+
+import org.junit.Assert;
+
+import java.util.List;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class QuadTreeSearchTest {
+    
+    private static final Logger LOGGER = LoggerFactory.getLogger(QuadTreeSearchTest.class);
+
+    private static QuadTree quadTree;
+
+    @BeforeClass
+    public static void setUp() {
+        Region area = new Region(0, 0, 400, 400);
+        quadTree = new QuadTree(area);
+
+        float[][] points = new float[][] { { 21, 25 }, { 55, 53 }, { 70, 318 }, { 98, 302 }, 
+            { 49, 229 }, { 135, 229 }, { 224, 292 }, { 206, 321 }, { 197, 258 }, { 245, 238 } };
+
+        for (int i = 0; i < points.length; i++) {
+            Point point = new Point(points[i][0], points[i][1]);
+            quadTree.addPoint(point);
+        }
+        LOGGER.debug("\n" + quadTree.printTree(""));
+        LOGGER.debug("==============================================");
+    }
+
+    @Test
+    public void givenQuadTree_whenSearchingForRange_thenReturn1MatchingItem() {
+        Region searchArea = new Region(200, 200, 250, 250);
+        List<Point> result = quadTree.search(searchArea, null, "");
+        LOGGER.debug(result.toString());
+        LOGGER.debug(quadTree.printSearchTraversePath());
+       
+        Assert.assertEquals(1, result.size());
+        Assert.assertArrayEquals(new float[] { 245, 238 }, 
+            new float[]{result.get(0).getX(), result.get(0).getY() }, 0);
+    }
+    
+    @Test
+    public void givenQuadTree_whenSearchingForRange_thenReturn2MatchingItems() {
+        Region searchArea = new Region(0, 0, 100, 100);
+        List<Point> result = quadTree.search(searchArea, null, "");
+        LOGGER.debug(result.toString());
+        LOGGER.debug(quadTree.printSearchTraversePath());
+        
+        Assert.assertEquals(2, result.size());
+        Assert.assertArrayEquals(new float[] { 21, 25 }, 
+            new float[]{result.get(0).getX(), result.get(0).getY() }, 0);
+        Assert.assertArrayEquals(new float[] { 55, 53 }, 
+            new float[]{result.get(1).getX(), result.get(1).getY() }, 0);
+        
+    }
+}