Merge pull request #14 from eugenp/master

update
2019-12-29 22:16:05 +01:00
parent 91633ff4cf 9b35c6194f
commit ee7316bdea
1383 changed files with 6266 additions and 2640 deletions
@@ -39,7 +39,6 @@ target/
 spring-openid/src/main/resources/application.properties
 .recommenders/
 /spring-hibernate4/nbproject/
-spring-security-openid/src/main/resources/application.properties

 spring-all/*.log

@@ -15,5 +15,4 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Creating a Triangle with for Loops in Java](https://www.baeldung.com/java-print-triangle)
 - [Efficient Word Frequency Calculator in Java](https://www.baeldung.com/java-word-frequency)
 - [The K-Means Clustering Algorithm in Java](https://www.baeldung.com/java-k-means-clustering-algorithm)
- [Creating a Custom Annotation in Java](https://www.baeldung.com/java-custom-annotation)
 - More articles: [[<-- prev]](/algorithms-miscellaneous-2) [[next -->]](/algorithms-miscellaneous-4)
@@ -10,4 +10,6 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Find If Two Numbers Are Relatively Prime in Java](https://www.baeldung.com/java-two-relatively-prime-numbers)
 - [Knapsack Problem Implementation in Java](https://www.baeldung.com/java-knapsack)
 - [How to Determine if a Binary Tree is Balanced](https://www.baeldung.com/java-balanced-binary-tree)
+- [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
+- [Overview of Combinatorial Problems in Java](https://www.baeldung.com/java-combinatorial-algorithms)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-4)
@@ -34,6 +34,11 @@
            <artifactId>tradukisto</artifactId>
            <version>${tradukisto.version}</version>
        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>28.1-jre</version>
+        </dependency>

        <dependency>
            <groupId>org.assertj</groupId>
@@ -0,0 +1,20 @@
+package com.baeldung.algorithms.greedy;
+
+import lombok.Getter;
+
+public class Follower {
+
+    @Getter String username;
+    @Getter long count;
+    
+    public Follower(String username, long count) {
+        super();
+        this.username = username;
+        this.count = count;
+    }
+    
+    @Override
+    public String toString() {
+        return "User: " + username + ", Followers: " + count + "\n\r" ; 
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FollowersPath {
+
+    private List<Follower> accounts;
+    private long count;
+    
+    public FollowersPath() {
+        super();
+        this.accounts = new ArrayList<>();
+    }
+    
+    public List<Follower> getAccounts() {
+        return accounts;
+    }
+    public long getCount() {
+        return count;
+    }
+    
+    public void addFollower(String username, long count) {
+        accounts.add(new Follower(username, count));
+    }
+    
+    public void addCount(long count) {
+        this.count += count;
+    }
+    
+    @Override
+    public String toString() {
+        String details = "";
+        for(Follower a : accounts) {
+            details+=a.toString() + ", ";
+        }
+        
+        return "Total: " + count + ", \n\r" +
+                " Details: { " + "\n\r" + 
+                details + "\n\r" + 
+                " }";
+    }
+    
+}
@@ -0,0 +1,47 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class GreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector sc;
+    FollowersPath fp;
+    
+    public GreedyAlgorithm(SocialConnector sc) {
+        super();
+        this.sc = sc;
+        this.fp = new FollowersPath();
+    }
+    
+    public long findMostFollowersPath(String account) throws Exception {        
+        long max = 0;
+        SocialUser toFollow = null;
+        
+        List<SocialUser> followers = sc.getFollowers(account);
+        for (SocialUser el : followers) {
+            long followersCount = el.getFollowersCount();
+            if (followersCount > max) {
+                toFollow = el;
+                max = followersCount;
+            }
+        }
+        
+        if (currentLevel < maxLevel - 1) {
+            currentLevel++;
+            max += findMostFollowersPath(toFollow.getUsername());
+            //fp.addFollower(toFollow.getUsername(), max);
+            //fp.addCount(max);
+            return max;
+        } else {
+            //fp.addFollower(toFollow.getUsername(), max);
+            //fp.addCount(max);
+            return max;
+        }            
+    }
+    
+    public FollowersPath getFollowers() {
+        return fp;
+    }
+}
@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.List;
+
+public class NonGreedyAlgorithm {
+
+    int currentLevel = 0;
+    final int maxLevel = 3; 
+    SocialConnector tc;
+    
+    public NonGreedyAlgorithm(SocialConnector tc, int level) {
+        super();
+        this.tc = tc;
+        this.currentLevel = level;
+    }
+    
+    
+    public long findMostFollowersPath(String account) throws Exception {        
+        List<SocialUser> followers = tc.getFollowers(account);
+        long total = currentLevel > 0 ? followers.size() : 0;
+
+        if (currentLevel < maxLevel ) {
+            currentLevel++;
+
+            long[] count = new long[followers.size()];
+            int i = 0;
+            for (SocialUser el : followers) {
+                NonGreedyAlgorithm sub = new NonGreedyAlgorithm(tc, currentLevel);
+                count[i] = sub.findMostFollowersPath(el.getUsername());
+                i++;
+            }
+            
+            long max = 0;
+            for (; i > 0; i--) {
+                if (count[i-1] > max )
+                    max = count[i-1];
+            }
+            
+            return total + max;
+        }
+        
+        return total;
+    }
+}
@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+import lombok.Setter;
+
+public class SocialConnector {
+    private boolean isCounterEnabled = true;
+    private int counter = 4;
+    @Getter @Setter List<SocialUser> users;
+    
+    public SocialConnector() {
+        users = new ArrayList<>();
+    }
+    
+    public boolean switchCounter() {
+        this.isCounterEnabled = !this.isCounterEnabled;
+        return this.isCounterEnabled;
+    }
+    
+    public List<SocialUser> getFollowers(String account) throws Exception {
+        if (counter < 0)
+            throw new Exception ("API limit reached");
+        else {
+            if(this.isCounterEnabled) counter--;
+            for(SocialUser user : users) {
+                if (user.getUsername().equals(account)) {
+                    return user.getFollowers();
+                }
+            }
+        }
+        return new ArrayList<>();
+    }
+}
@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.greedy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import lombok.Getter;
+
+public class SocialUser {
+
+    @Getter private String username;
+    @Getter private List<SocialUser> followers;
+
+    public SocialUser(String username) {
+        super();
+        this.username = username;
+        this.followers = new ArrayList<>();
+    }
+    
+    public SocialUser(String username, List<SocialUser> followers) {
+        super();
+        this.username = username;
+        this.followers = followers;
+    }
+    
+    public long getFollowersCount() {
+        return followers.size();
+    }
+    
+    public void addFollowers(List<SocialUser> followers) {
+        this.followers.addAll(followers);
+    }
+    
+    @Override
+    public boolean equals(Object obj) {
+        return ((SocialUser) obj).getUsername().equals(username);
+    }
+    
+}
@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static java.util.Comparator.reverseOrder;
+
+public class MedianOfIntegerStream {
+
+    private Queue<Integer> minHeap, maxHeap;
+
+    MedianOfIntegerStream() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>(reverseOrder());
+    }
+
+    void add(int num) {
+        if (!minHeap.isEmpty() && num < minHeap.peek()) {
+            maxHeap.offer(num);
+            if (maxHeap.size() > minHeap.size() + 1) {
+                minHeap.offer(maxHeap.poll());
+            }
+        } else {
+            minHeap.offer(num);
+            if (minHeap.size() > maxHeap.size() + 1) {
+                maxHeap.offer(minHeap.poll());
+            }
+        }
+    }
+
+    double getMedian() {
+        int median;
+        if (minHeap.size() < maxHeap.size()) {
+            median = maxHeap.peek();
+        } else if (minHeap.size() > maxHeap.size()) {
+            median = minHeap.peek();
+        } else {
+            median = (minHeap.peek() + maxHeap.peek()) / 2;
+        }
+        return median;
+    }
+}
@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import java.util.PriorityQueue;
+import java.util.Queue;
+
+import static java.util.Comparator.reverseOrder;
+
+public class MedianOfIntegerStream2 {
+
+    private Queue<Integer> minHeap, maxHeap;
+
+    MedianOfIntegerStream2() {
+        minHeap = new PriorityQueue<>();
+        maxHeap = new PriorityQueue<>(reverseOrder());
+    }
+
+    void add(int num) {
+        if (minHeap.size() == maxHeap.size()) {
+            maxHeap.offer(num);
+            minHeap.offer(maxHeap.poll());
+        } else {
+            minHeap.offer(num);
+            maxHeap.offer(minHeap.poll());
+        }
+    }
+
+    double getMedian() {
+        int median;
+        if (minHeap.size() > maxHeap.size()) {
+            median = minHeap.peek();
+        } else {
+            median = (minHeap.peek() + maxHeap.peek()) / 2;
+        }
+        return median;
+    }
+}
@@ -0,0 +1,72 @@
+package com.baeldung.algorithms.kruskal;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class CycleDetector {
+
+    List<DisjointSetInfo> nodes;
+
+    public CycleDetector(int totalNodes) {
+        initDisjointSets(totalNodes);
+    }
+
+    public boolean detectCycle(Integer u, Integer v) {
+        Integer rootU = pathCompressionFind(u);
+        Integer rootV = pathCompressionFind(v);
+        if (rootU.equals(rootV)) {
+            return true;
+        }
+        unionByRank(rootU, rootV);
+        return false;
+    }
+
+    private void initDisjointSets(int totalNodes) {
+        nodes = new ArrayList<>(totalNodes);
+        for (int i = 0; i < totalNodes; i++) {
+            nodes.add(new DisjointSetInfo(i));
+        }
+    }
+
+    private Integer find(Integer node) {
+        Integer parent = nodes.get(node).getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            return find(parent);
+        }
+    }
+
+    private Integer pathCompressionFind(Integer node) {
+        DisjointSetInfo setInfo = nodes.get(node);
+        Integer parent = setInfo.getParentNode();
+        if (parent.equals(node)) {
+            return node;
+        } else {
+            Integer parentNode = find(parent);
+            setInfo.setParentNode(parentNode);
+            return parentNode;
+        }
+    }
+
+    private void union(Integer rootU, Integer rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        setInfoU.setParentNode(rootV);
+    }
+
+    private void unionByRank(int rootU, int rootV) {
+        DisjointSetInfo setInfoU = nodes.get(rootU);
+        DisjointSetInfo setInfoV = nodes.get(rootV);
+        int rankU = setInfoU.getRank();
+        int rankV = setInfoV.getRank();
+        if (rankU < rankV) {
+            setInfoU.setParentNode(rootV);
+        } else {
+            setInfoV.setParentNode(rootU);
+            if (rankU == rankV) {
+                setInfoU.setRank(rankU + 1);
+            }
+        }
+    }
+
+}
@@ -0,0 +1,28 @@
+package com.baeldung.algorithms.kruskal;
+
+public class DisjointSetInfo {
+
+    private Integer parentNode;
+    private int rank;
+
+    DisjointSetInfo(Integer nodeNumber) {
+        setParentNode(nodeNumber);
+        setRank(1);
+    }
+
+    public Integer getParentNode() {
+        return parentNode;
+    }
+
+    public void setParentNode(Integer parentNode) {
+        this.parentNode = parentNode;
+    }
+
+    public int getRank() {
+        return rank;
+    }
+
+    public void setRank(int rank) {
+        this.rank = rank;
+    }
+}
@@ -0,0 +1,53 @@
+package com.baeldung.algorithms.kruskal;
+
+import com.google.common.graph.EndpointPair;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Set;
+
+public class Kruskal {
+
+    public ValueGraph<Integer, Double> minSpanningTree(ValueGraph<Integer, Double> graph) {
+
+        return spanningTree(graph, true);
+    }
+
+    public ValueGraph<Integer, Double> maxSpanningTree(ValueGraph<Integer, Double> graph) {
+        return spanningTree(graph, false);
+    }
+
+    private ValueGraph<Integer, Double> spanningTree(ValueGraph<Integer, Double> graph, boolean minSpanningTree) {
+        Set<EndpointPair<Integer>> edges = graph.edges();
+        List<EndpointPair<Integer>> edgeList = new ArrayList<>(edges);
+
+        if (minSpanningTree) {
+            edgeList.sort(Comparator.comparing(e -> graph.edgeValue(e).get()));
+        } else {
+            edgeList.sort(Collections.reverseOrder(Comparator.comparing(e -> graph.edgeValue(e).get())));
+        }
+
+        int totalNodes = graph.nodes().size();
+        CycleDetector cycleDetector = new CycleDetector(totalNodes);
+        int edgeCount = 0;
+
+        MutableValueGraph<Integer, Double> spanningTree = ValueGraphBuilder.undirected().build();
+        for (EndpointPair<Integer> edge : edgeList) {
+            if (cycleDetector.detectCycle(edge.nodeU(), edge.nodeV())) {
+                continue;
+            }
+            spanningTree.putEdgeValue(edge.nodeU(), edge.nodeV(), graph.edgeValue(edge).get());
+            edgeCount++;
+            if (edgeCount == totalNodes - 1) {
+                break;
+            }
+        }
+        return spanningTree;
+    }
+
+}
@@ -0,0 +1,58 @@
+package com.baeldung.algorithms.greedy;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class GreedyAlgorithmUnitTest {
+
+    private SocialConnector prepareNetwork() {
+        SocialConnector sc = new SocialConnector();
+        SocialUser root = new SocialUser("root");
+        SocialUser child1 = new SocialUser("child1");
+        SocialUser child2 = new SocialUser("child2");
+        SocialUser child3 = new SocialUser("child3");
+        SocialUser child21 = new SocialUser("child21");
+        SocialUser child211 = new SocialUser("child211");
+        SocialUser child2111 = new SocialUser("child2111");
+        SocialUser child31 = new SocialUser("child31");
+        SocialUser child311 = new SocialUser("child311");
+        SocialUser child3111 = new SocialUser("child3111");
+        child211.addFollowers(Arrays.asList(new SocialUser[]{child2111}));
+        child311.addFollowers(Arrays.asList(new SocialUser[]{child3111}));
+        child21.addFollowers(Arrays.asList(new SocialUser[]{child211}));
+        child31.addFollowers(Arrays.asList(new SocialUser[]{child311, 
+          new SocialUser("child312"), new SocialUser("child313"), new SocialUser("child314")}));
+        child1.addFollowers(Arrays.asList(new SocialUser[]{new SocialUser("child11"), new SocialUser("child12")}));
+        child2.addFollowers(Arrays.asList(new SocialUser[]{child21, new SocialUser("child22"), new SocialUser("child23")}));
+        child3.addFollowers(Arrays.asList(new SocialUser[]{child31}));
+        root.addFollowers(Arrays.asList(new SocialUser[]{child1, child2, child3}));
+        sc.setUsers(Arrays.asList(new SocialUser[]{root, child1, child2, child3, child21, child31, child311, child211}));
+        return sc;
+    }
+
+    @Test
+    public void greedyAlgorithmTest() throws Exception {
+        GreedyAlgorithm ga = new GreedyAlgorithm(prepareNetwork());
+        assertEquals(ga.findMostFollowersPath("root"), 5);
+    }
+
+    @Test
+    public void nongreedyAlgorithmTest() throws Exception {
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(prepareNetwork(), 0);
+        Assertions.assertThrows(Exception.class, () -> {
+            nga.findMostFollowersPath("root");
+          });
+    }
+
+    @Test
+    public void nongreedyAlgorithmUnboundedTest() throws Exception {
+        SocialConnector sc = prepareNetwork();
+        sc.switchCounter();
+        NonGreedyAlgorithm nga = new NonGreedyAlgorithm(sc, 0);
+        assertEquals(nga.findMostFollowersPath("root"), 6);
+    }
+}
@@ -0,0 +1,41 @@
+package com.baeldung.algorithms.integerstreammedian;
+
+import org.junit.Test;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+
+public class MedianOfIntegerStreamUnitTest {
+
+    @Test
+    public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach1() {
+        MedianOfIntegerStream mis = new MedianOfIntegerStream();
+        for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
+            mis.add(e.getKey());
+            assertEquals(e.getValue(), (Double) mis.getMedian());
+        }
+    }
+
+    @Test
+    public void givenStreamOfIntegers_whenAnElementIsRead_thenMedianChangesWithApproach2() {
+        MedianOfIntegerStream2 mis = new MedianOfIntegerStream2();
+        for (Map.Entry<Integer, Double> e : testcaseFixture().entrySet()) {
+            mis.add(e.getKey());
+            assertEquals(e.getValue(), (Double) mis.getMedian());
+        }
+    }
+
+    private Map<Integer, Double> testcaseFixture() {
+        return new LinkedHashMap<Integer, Double>() {{
+            put(1, 1d);
+            put(7, 4d);
+            put(5, 5d);
+            put(8, 6d);
+            put(3, 5d);
+            put(9, 6d);
+            put(4, 5d);
+        }};
+    }
+}
@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.kruskal;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Before;
+import org.junit.Test;
+import com.google.common.graph.MutableValueGraph;
+import com.google.common.graph.ValueGraph;
+import com.google.common.graph.ValueGraphBuilder;
+import com.baeldung.algorithms.kruskal.Kruskal;
+
+public class KruskalUnitTest {
+
+    private MutableValueGraph<Integer, Double> graph;
+
+    @Before
+    public void setup() {
+        graph = ValueGraphBuilder.undirected().build();
+        graph.putEdgeValue(0, 1, 8.0);
+        graph.putEdgeValue(0, 2, 5.0);
+        graph.putEdgeValue(1, 2, 9.0);
+        graph.putEdgeValue(1, 3, 11.0);
+        graph.putEdgeValue(2, 3, 15.0);
+        graph.putEdgeValue(2, 4, 10.0);
+        graph.putEdgeValue(3, 4, 7.0);
+    }
+
+    @Test
+    public void givenGraph_whenMinimumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.minSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(0, 2));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertTrue(spanningTree.hasEdgeConnecting(3, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(0, 2), spanningTree.edgeValue(0, 2));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+        assertEquals(graph.edgeValue(3, 4), spanningTree.edgeValue(3, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 3));
+        assertFalse(spanningTree.hasEdgeConnecting(2, 3));
+    }
+
+    @Test
+    public void givenGraph_whenMaximumSpanningTree_thenOutputCorrectResult() {
+        final Kruskal kruskal = new Kruskal();
+        ValueGraph<Integer, Double> spanningTree = kruskal.maxSpanningTree(graph);
+
+        assertTrue(spanningTree.hasEdgeConnecting(0, 1));
+        assertTrue(spanningTree.hasEdgeConnecting(1, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 3));
+        assertTrue(spanningTree.hasEdgeConnecting(2, 4));
+        assertEquals(graph.edgeValue(0, 1), spanningTree.edgeValue(0, 1));
+        assertEquals(graph.edgeValue(1, 3), spanningTree.edgeValue(1, 3));
+        assertEquals(graph.edgeValue(2, 3), spanningTree.edgeValue(2, 3));
+        assertEquals(graph.edgeValue(2, 4), spanningTree.edgeValue(2, 4));
+
+        assertFalse(spanningTree.hasEdgeConnecting(0, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(1, 2));
+        assertFalse(spanningTree.hasEdgeConnecting(3, 4));
+    }
+}
@@ -9,3 +9,4 @@ This module contains articles about searching algorithms.
 - [Breadth-First Search Algorithm in Java](https://www.baeldung.com/java-breadth-first-search)
 - [String Search Algorithms for Large Texts](https://www.baeldung.com/java-full-text-search-algorithms)
 - [Monte Carlo Tree Search for Tic-Tac-Toe Game](https://www.baeldung.com/java-monte-carlo-tree-search)
+- [Range Search Algorithm in Java](https://www.baeldung.com/java-range-search)
@@ -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 + "]";
+    }
+}
@@ -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();
+    }
+}
@@ -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;
+    }
+
+}
@@ -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 QuadTreeSearchUnitTest {
+    
+    private static final Logger LOGGER = LoggerFactory.getLogger(QuadTreeSearchUnitTest.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.info("\n" + quadTree.printTree(""));
+        LOGGER.info("==============================================");
+    }
+
+    @Test
+    public void givenQuadTree_whenSearchingForRange_thenReturn1MatchingItem() {
+        Region searchArea = new Region(200, 200, 250, 250);
+        List<Point> result = quadTree.search(searchArea, null, "");
+        LOGGER.info(result.toString());
+        LOGGER.info(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.info(result.toString());
+        LOGGER.info(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);
+        
+    }
+}
@@ -16,7 +16,7 @@
    </context-param>
    <context-param>
        <param-name>contextConfigLocation</param-name>
-        <param-value>org.baeldung.config</param-value>
+        <param-value>com.baeldung.config</param-value>
    </context-param>

    <listener>
@@ -1,4 +1,4 @@
-package org.baeldung.java;
+package com.baeldung.java;

 import java.io.BufferedOutputStream;
 import java.io.File;
@@ -1,4 +1,4 @@
-package org.baeldung.java;
+package com.baeldung.java;

 import java.io.BufferedOutputStream;
 import java.io.BufferedReader;
@@ -3,7 +3,7 @@
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
-    <groupId>org.baeldung.examples.olingo2</groupId>
+    <groupId>com.baeldung.examples.olingo2</groupId>
    <artifactId>olingo2</artifactId>
    <name>olingo2</name>
    <description>Sample Olingo 2 Project</description>
@@ -1,4 +1,4 @@
-package org.baeldung.examples.olingo2;
+package com.baeldung.examples.olingo2;

 import java.util.List;
 import java.util.Map;
@@ -9,10 +9,8 @@ import javax.persistence.EntityManagerFactory;
 import javax.persistence.EntityTransaction;
 import javax.persistence.FlushModeType;
 import javax.persistence.LockModeType;
-import javax.persistence.Persistence;
 import javax.persistence.Query;
 import javax.persistence.StoredProcedureQuery;
-import javax.persistence.SynchronizationType;
 import javax.persistence.TypedQuery;
 import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaDelete;
@@ -25,11 +23,8 @@ import org.apache.olingo.odata2.api.processor.ODataContext;
 import org.apache.olingo.odata2.jpa.processor.api.ODataJPAContext;
 import org.apache.olingo.odata2.jpa.processor.api.ODataJPAServiceFactory;
 import org.apache.olingo.odata2.jpa.processor.api.exception.ODataJPARuntimeException;
-import org.baeldung.examples.olingo2.JerseyConfig.EntityManagerFilter;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import org.springframework.orm.jpa.EntityManagerFactoryUtils;
-import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
 import org.springframework.stereotype.Component;

 /**
@@ -58,7 +53,7 @@ public class CarsODataJPAServiceFactory extends ODataJPAServiceFactory {
        ODataJPAContext ctx = getODataJPAContext();
        ODataContext octx = ctx.getODataContext();
        HttpServletRequest request = (HttpServletRequest)octx.getParameter(ODataContext.HTTP_SERVLET_REQUEST_OBJECT);
-        EntityManager em = (EntityManager)request.getAttribute(EntityManagerFilter.EM_REQUEST_ATTRIBUTE);
+        EntityManager em = (EntityManager)request.getAttribute(JerseyConfig.EntityManagerFilter.EM_REQUEST_ATTRIBUTE);
                
        // Here we're passing the EM that was created by the EntityManagerFilter (see JerseyConfig)
        ctx.setEntityManager(new EntityManagerWrapper(em));
@@ -1,11 +1,10 @@
-    package org.baeldung.examples.olingo2;
+    package com.baeldung.examples.olingo2;

 import java.io.IOException;

 import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.EntityTransaction;
-import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
 import javax.ws.rs.ApplicationPath;
 import javax.ws.rs.Path;
@@ -1,8 +1,7 @@
-package org.baeldung.examples.olingo2;
+package com.baeldung.examples.olingo2;

 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
-import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

@SpringBootApplication
--- a/Show More
+++ b/Show More