Merge pull request #12 from eugenp/master

merge sync

.gitignore

@@ -65,6 +65,7 @@ core-java-io/target_link.txt
 core-java/src/main/java/com/baeldung/manifest/MANIFEST.MF
 ethereum/logs/
 jmeter/src/main/resources/*-JMeter.csv
+ninja/devDb.mv.db
 
 **/node_modules/
 **/dist

akka-http/src/test/java/com/baeldung/akkahttp/UserServerUnitTest.java

@@ -7,6 +7,8 @@ import akka.http.javadsl.model.HttpEntities;
 import akka.http.javadsl.model.HttpRequest;
 import akka.http.javadsl.testkit.JUnitRouteTest;
 import akka.http.javadsl.testkit.TestRoute;
+
+import org.junit.Ignore;
 import org.junit.Test;
 
 public class UserServerUnitTest extends JUnitRouteTest {
@@ -17,6 +19,7 @@ public class UserServerUnitTest extends JUnitRouteTest {
 
   TestRoute appRoute = testRoute(new UserServer(userActorRef).routes());
 
+  @Ignore
   @Test
   public void whenRequest_thenActorResponds() {
 
@@ -28,10 +31,10 @@ public class UserServerUnitTest extends JUnitRouteTest {
             .assertStatusCode(404);
 
     appRoute.run(HttpRequest.DELETE("/users/1"))
-            .assertStatusCode(200);
+            .assertStatusCode(405);
 
     appRoute.run(HttpRequest.DELETE("/users/42"))
-            .assertStatusCode(200);
+            .assertStatusCode(405);
 
     appRoute.run(HttpRequest.POST("/users")
             .withEntity(HttpEntities.create(ContentTypes.APPLICATION_JSON, zaphod())))

algorithms-miscellaneous-1/pom.xml

@@ -64,7 +64,7 @@
             <plugin>
                 <groupId>org.codehaus.mojo</groupId>
                 <artifactId>cobertura-maven-plugin</artifactId>
-                <version>2.7</version>
+                <version>${cobertura.plugin.version}</version>
                 <configuration>
                     <instrumentation>
                         <ignores>
@@ -85,6 +85,7 @@
         <commons-codec.version>1.11</commons-codec.version>
         <guava.version>27.0.1-jre</guava.version>
         <combinatoricslib3.version>3.3.0</combinatoricslib3.version>
+        <cobertura.plugin.version>2.7</cobertura.plugin.version>
     </properties>
 
 </project>

algorithms-miscellaneous-2/README.md

@@ -13,4 +13,5 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [Create a Sudoku Solver in Java](https://www.baeldung.com/java-sudoku)
 - [Displaying Money Amounts in Words](https://www.baeldung.com/java-money-into-words)
 - [A Collaborative Filtering Recommendation System in Java](https://www.baeldung.com/java-collaborative-filtering-recommendations)
+- [Implementing A* Pathfinding in Java](https://www.baeldung.com/java-a-star-pathfinding)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-1) [[next -->]](/../algorithms-miscellaneous-3)

algorithms-miscellaneous-2/src/main/java/com/baeldung/algorithms/slope_one/SlopeOne.java

@@ -98,7 +98,7 @@ public class SlopeOne {
             for (Item j : InputData.items) {
                 if (e.getValue().containsKey(j)) {
                     clean.put(j, e.getValue().get(j));
-                } else {
+                } else if (!clean.containsKey(j)) {
                     clean.put(j, -1.0);
                 }
             }

algorithms-miscellaneous-3/pom.xml

@@ -46,13 +46,13 @@
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
-            <version>3.8.1</version>
+            <version>${commons.lang3.version}</version>
         </dependency>
 
         <dependency>
             <groupId>pl.pragmatists</groupId>
             <artifactId>JUnitParams</artifactId>
-            <version>1.1.0</version>
+            <version>${JUnitParams.version}</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -91,6 +91,8 @@
         <retrofit.version>2.6.0</retrofit.version>
         <jmh-core.version>1.19</jmh-core.version>
         <jmh-generator.version>1.19</jmh-generator.version>
+        <commons.lang3.version>3.8.1</commons.lang3.version>
+        <JUnitParams.version>1.1.0</JUnitParams.version>
     </properties>
 
 </project>

algorithms-miscellaneous-5/README.md

@@ -12,4 +12,12 @@ This module contains articles about algorithms. Some classes of algorithms, e.g.
 - [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)
+- [Prim’s Algorithm](https://www.baeldung.com/java-prim-algorithm)
+- [Maximum Subarray Problem](https://www.baeldung.com/java-maximum-subarray)
+- [How to Merge Two Sorted Arrays](https://www.baeldung.com/java-merge-sorted-arrays)
+- [Median of Stream of Integers using Heap](https://www.baeldung.com/java-stream-integers-median-using-heap)
+- [Kruskal’s Algorithm for Spanning Trees](https://www.baeldung.com/java-spanning-trees-kruskal)
+- [Balanced Brackets Algorithm in Java](https://www.baeldung.com/java-balanced-brackets-algorithm)
+- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
+- [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-4)

algorithms-miscellaneous-5/pom.xml

@@ -37,7 +37,7 @@
         <dependency>
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
-            <version>28.1-jre</version>
+            <version>${guava.version}</version>
         </dependency>
 
         <dependency>
@@ -65,6 +65,7 @@
         <org.assertj.core.version>3.9.0</org.assertj.core.version>
         <commons-codec.version>1.11</commons-codec.version>
         <commons-math3.version>3.6.1</commons-math3.version>
+        <guava.version>28.1-jre</guava.version>
     </properties>
 
 </project>

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbinarytree/AVLTree.java

@@ -0,0 +1,141 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+public class AVLTree {
+
+    public class Node {
+        int key;
+        int height;
+        Node left;
+        Node right;
+
+        Node(int key) {
+            this.key = key;
+        }
+    }
+
+    private Node root;
+
+    public Node find(int key) {
+        Node current = root;
+        while (current != null) {
+            if (current.key == key) {
+               break;
+            }
+            current = current.key < key ? current.right : current.left;
+        }
+        return current;
+    }
+
+    public void insert(int key) {
+        root = insert(root, key);
+    }
+
+    public void delete(int key) {
+        root = delete(root, key);
+    }
+
+    public Node getRoot() {
+        return root;
+    }
+
+    public int height() {
+        return root == null ? -1 : root.height;
+    }
+
+    private Node insert(Node node, int key) {
+        if (node == null) {
+            return new Node(key);
+        } else if (node.key > key) {
+            node.left = insert(node.left, key);
+        } else if (node.key < key) {
+            node.right = insert(node.right, key);
+        } else {
+            throw new RuntimeException("duplicate Key!");
+        }
+        return rebalance(node);
+    }
+
+    private Node delete(Node node, int key) {
+        if (node == null) {
+            return node;
+        } else if (node.key > key) {
+            node.left = delete(node.left, key);
+        } else if (node.key < key) {
+            node.right = delete(node.right, key);
+        } else {
+            if (node.left == null || node.right == null) {
+                node = (node.left == null) ? node.right : node.left;
+            } else {
+                Node mostLeftChild = mostLeftChild(node.right);
+                node.key = mostLeftChild.key;
+                node.right = delete(node.right, node.key);
+            }
+        }
+        if (node != null) {
+            node = rebalance(node);
+        }
+        return node;
+    }
+
+    private Node mostLeftChild(Node node) {
+        Node current = node;
+        /* loop down to find the leftmost leaf */
+        while (current.left != null) {
+            current = current.left;
+        }
+        return current;
+    }
+
+    private Node rebalance(Node z) {
+        updateHeight(z);
+        int balance = getBalance(z);
+        if (balance > 1) {
+            if (height(z.right.right) > height(z.right.left)) {
+                z = rotateLeft(z);
+            } else {
+                z.right = rotateRight(z.right);
+                z = rotateLeft(z);
+            }
+        } else if (balance < -1) {
+            if (height(z.left.left) > height(z.left.right)) {
+                z = rotateRight(z);
+            } else {
+                z.left = rotateLeft(z.left);
+                z = rotateRight(z);
+            }
+        }
+        return z;
+    }
+
+    private Node rotateRight(Node y) {
+        Node x = y.left;
+        Node z = x.right;
+        x.right = y;
+        y.left = z;
+        updateHeight(y);
+        updateHeight(x);
+        return x;
+    }
+
+    private Node rotateLeft(Node y) {
+        Node x = y.right;
+        Node z = x.left;
+        x.left = y;
+        y.right = z;
+        updateHeight(y);
+        updateHeight(x);
+        return x;
+    }
+
+    private void updateHeight(Node n) {
+        n.height = 1 + Math.max(height(n.left), height(n.right));
+    }
+
+    private int height(Node n) {
+        return n == null ? -1 : n.height;
+    }
+
+    public int getBalance(Node n) {
+        return (n == null) ? 0 : height(n.right) - height(n.left);
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDeque.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import java.util.Deque;
+import java.util.LinkedList;
+
+public class BalancedBracketsUsingDeque {
+
+    public boolean isBalanced(String str) {
+        if (null == str || ((str.length() % 2) != 0)) {
+            return false;
+        } else {
+            char[] ch = str.toCharArray();
+            for (char c : ch) {
+                if (!(c == '{' || c == '[' || c == '(' || c == '}' || c == ']' || c == ')')) {
+                    return false;
+                }
+
+            }
+        }
+
+        Deque<Character> deque = new LinkedList<>();
+        for (char ch : str.toCharArray()) {
+            if (ch == '{' || ch == '[' || ch == '(') {
+                deque.addFirst(ch);
+            } else {
+                if (!deque.isEmpty() && ((deque.peekFirst() == '{' && ch == '}') || (deque.peekFirst() == '[' && ch == ']') || (deque.peekFirst() == '(' && ch == ')'))) {
+                    deque.removeFirst();
+                } else {
+                    return false;
+                }
+            }
+        }
+
+        return true;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingString.java

@@ -0,0 +1,27 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+public class BalancedBracketsUsingString {
+
+    public boolean isBalanced(String str) {
+        if (null == str || ((str.length() % 2) != 0)) {
+            return false;
+        } else {
+            char[] ch = str.toCharArray();
+            for (char c : ch) {
+                if (!(c == '{' || c == '[' || c == '(' || c == '}' || c == ']' || c == ')')) {
+                    return false;
+                }
+
+            }
+        }
+
+        while (str.contains("()") || str.contains("[]") || str.contains("{}")) {
+            str = str.replaceAll("\\(\\)", "")
+                .replaceAll("\\[\\]", "")
+                .replaceAll("\\{\\}", "");
+        }
+        return (str.length() == 0);
+
+    }
+
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/GreedyAlgorithm.java

@@ -15,7 +15,7 @@ public class GreedyAlgorithm {
         this.fp = new FollowersPath();
     }
     
-    public long findMostFollowersPath(String account) throws Exception {        
+    public long findMostFollowersPath(String account) {
         long max = 0;
         SocialUser toFollow = null;
         
@@ -31,12 +31,8 @@ public class GreedyAlgorithm {
         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;
         }            
     }

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/NonGreedyAlgorithm.java

@@ -13,9 +13,8 @@ public class NonGreedyAlgorithm {
         this.tc = tc;
         this.currentLevel = level;
     }
-    
+      
-    
+    public long findMostFollowersPath(String account) {
-    public long findMostFollowersPath(String account) throws Exception {        
         List<SocialUser> followers = tc.getFollowers(account);
         long total = currentLevel > 0 ? followers.size() : 0;
 

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/greedy/SocialConnector.java

@@ -20,9 +20,9 @@ public class SocialConnector {
         return this.isCounterEnabled;
     }
     
-    public List<SocialUser> getFollowers(String account) throws Exception {
+    public List<SocialUser> getFollowers(String account) {
         if (counter < 0)
-            throw new Exception ("API limit reached");
+            throw new IllegalStateException ("API limit reached");
         else {
             if(this.isCounterEnabled) counter--;
             for(SocialUser user : users) {

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/minheapmerge/HeapNode.java

@@ -0,0 +1,13 @@
+package com.baeldung.algorithms.minheapmerge;
+
+public class HeapNode {
+
+    int element;
+    int arrayIndex;
+    int nextElementIndex = 1;
+
+    public HeapNode(int element, int arrayIndex) {
+        this.element = element;
+        this.arrayIndex = arrayIndex;
+    }
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/minheapmerge/MinHeap.java

@@ -0,0 +1,88 @@
+package com.baeldung.algorithms.minheapmerge;
+
+public class MinHeap {
+
+    HeapNode[] heapNodes;
+
+    public MinHeap(HeapNode heapNodes[]) {
+        this.heapNodes = heapNodes;
+        heapifyFromLastLeafsParent();
+    }
+
+    void heapifyFromLastLeafsParent() {
+        int lastLeafsParentIndex = getParentNodeIndex(heapNodes.length);
+        while (lastLeafsParentIndex >= 0) {
+            heapify(lastLeafsParentIndex);
+            lastLeafsParentIndex--;
+        }
+    }
+
+    void heapify(int index) {
+        int leftNodeIndex = getLeftNodeIndex(index);
+        int rightNodeIndex = getRightNodeIndex(index);
+        int smallestElementIndex = index;
+        if (leftNodeIndex < heapNodes.length && heapNodes[leftNodeIndex].element < heapNodes[index].element) {
+            smallestElementIndex = leftNodeIndex;
+        }
+        if (rightNodeIndex < heapNodes.length && heapNodes[rightNodeIndex].element < heapNodes[smallestElementIndex].element) {
+            smallestElementIndex = rightNodeIndex;
+        }
+        if (smallestElementIndex != index) {
+            swap(index, smallestElementIndex);
+            heapify(smallestElementIndex);
+        }
+    }
+
+    int getParentNodeIndex(int index) {
+        return (index - 1) / 2;
+    }
+
+    int getLeftNodeIndex(int index) {
+        return (2 * index + 1);
+    }
+
+    int getRightNodeIndex(int index) {
+        return (2 * index + 2);
+    }
+
+    HeapNode getRootNode() {
+        return heapNodes[0];
+    }
+
+    void heapifyFromRoot() {
+        heapify(0);
+    }
+
+    void swap(int i, int j) {
+        HeapNode temp = heapNodes[i];
+        heapNodes[i] = heapNodes[j];
+        heapNodes[j] = temp;
+    }
+    
+    static int[] merge(int[][] array) {
+        HeapNode[] heapNodes = new HeapNode[array.length];
+        int resultingArraySize = 0;
+
+        for (int i = 0; i < array.length; i++) {
+            HeapNode node = new HeapNode(array[i][0], i);
+            heapNodes[i] = node;
+            resultingArraySize += array[i].length;
+        }
+        
+        MinHeap minHeap = new MinHeap(heapNodes);
+        int[] resultingArray = new int[resultingArraySize];
+
+        for (int i = 0; i < resultingArraySize; i++) {
+            HeapNode root = minHeap.getRootNode();
+            resultingArray[i] = root.element;
+
+            if (root.nextElementIndex < array[root.arrayIndex].length) {
+                root.element = array[root.arrayIndex][root.nextElementIndex++];
+            } else {
+                root.element = Integer.MAX_VALUE;
+            }
+            minHeap.heapifyFromRoot();
+        }
+        return resultingArray;
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbinarytree/AVLTreeUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class AVLTreeUnitTest {
+
+    @Test
+    public void givenEmptyTree_whenHeightCalled_shouldReturnMinus1() {
+        AVLTree tree = new AVLTree();
+        Assert.assertEquals(-1, tree.height());
+    }
+
+    @Test
+    public void givenEmptyTree_whenInsertCalled_heightShouldBeZero() {
+        AVLTree tree = new AVLTree();
+        tree.insert(1);
+        Assert.assertEquals(0, tree.height());
+    }
+
+    @Test
+    public void givenEmptyTree_whenInsertCalled_treeShouldBeAvl() {
+        AVLTree tree = new AVLTree();
+        tree.insert(1);
+        Assert.assertTrue(isAVL(tree));
+    }
+
+    @Test
+    public void givenSampleTree_whenInsertCalled_treeShouldBeAvl() {
+        AVLTree tree = getSampleAVLTree();
+        int newKey = 11;
+        tree.insert(newKey);
+        Assert.assertTrue(isAVL(tree));
+    }
+
+    @Test
+    public void givenSampleTree_whenFindExistingKeyCalled_shouldReturnMatchedNode() {
+        AVLTree tree = getSampleAVLTree();
+        int existingKey = 2;
+        AVLTree.Node result = tree.find(existingKey);
+        Assert.assertEquals(result.key, existingKey);
+    }
+
+    @Test
+    public void givenSampleTree_whenFindNotExistingKeyCalled_shouldReturnNull() {
+        AVLTree tree = getSampleAVLTree();
+        int notExistingKey = 11;
+        AVLTree.Node result = tree.find(notExistingKey);
+        Assert.assertNull(result);
+    }
+
+    @Test
+    public void givenEmptyTree_whenDeleteCalled_treeShouldBeAvl() {
+        AVLTree tree = new AVLTree();
+        tree.delete(1);
+        Assert.assertTrue(isAVL(tree));
+    }
+
+    @Test
+    public void givenSampleTree_whenDeleteCalled_treeShouldBeAvl() {
+        AVLTree tree = getSampleAVLTree();
+        tree.delete(1);
+        Assert.assertTrue(isAVL(tree, tree.getRoot()));
+    }
+
+    private boolean isAVL(AVLTree tree) {
+       return isAVL(tree, tree.getRoot());
+    }
+
+    private boolean isAVL(AVLTree tree, AVLTree.Node node) {
+        if ( node == null )
+            return true;
+        int balance = tree.getBalance(node);
+        return (balance <= 1 && balance >= -1) && isAVL(tree, node.left) && isAVL(tree, node.right);
+    }
+
+    private AVLTree getSampleAVLTree() {
+        AVLTree avlTree = new AVLTree();
+        for (int i = 0; i < 10; i++)
+            avlTree.insert(i);
+        return avlTree;
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingDequeUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BalancedBracketsUsingDequeUnitTest {
+    private BalancedBracketsUsingDeque balancedBracketsUsingDeque;
+
+    @Before
+    public void setup() {
+        balancedBracketsUsingDeque = new BalancedBracketsUsingDeque();
+    }
+
+    @Test
+    public void givenNullInput_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced(null);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEmptyString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenInvalidCharacterString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("abc[](){}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenOddLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[]()}}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{[(])}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{[()]}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{[[(())]]}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenAnotherBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{([])}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenUnBalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingDeque.isBalanced("{{)[](}}");
+        assertThat(result).isFalse();
+    }
+
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/balancedbrackets/BalancedBracketsUsingStringUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.algorithms.balancedbrackets;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BalancedBracketsUsingStringUnitTest {
+    private BalancedBracketsUsingString balancedBracketsUsingString;
+
+    @Before
+    public void setup() {
+        balancedBracketsUsingString = new BalancedBracketsUsingString();
+    }
+
+    @Test
+    public void givenNullInput_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced(null);
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEmptyString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenInvalidCharacterString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("abc[](){}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenOddLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[]()}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[]()}}}}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthUnbalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{[(])}");
+        assertThat(result).isFalse();
+    }
+
+    @Test
+    public void givenEvenLengthBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{[()]}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{[[(())]]}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenAnotherBalancedString_whenCheckingForBalance_shouldReturnTrue() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{([])}}");
+        assertThat(result).isTrue();
+    }
+
+    @Test
+    public void givenUnBalancedString_whenCheckingForBalance_shouldReturnFalse() {
+        boolean result = balancedBracketsUsingString.isBalanced("{{)[](}}");
+        assertThat(result).isFalse();
+    }
+
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/greedy/GreedyAlgorithmUnitTest.java

@@ -35,21 +35,21 @@ public class GreedyAlgorithmUnitTest {
     }
 
     @Test
-    public void greedyAlgorithmTest() throws Exception {
+    public void greedyAlgorithmTest() {
         GreedyAlgorithm ga = new GreedyAlgorithm(prepareNetwork());
         assertEquals(ga.findMostFollowersPath("root"), 5);
     }
 
     @Test
-    public void nongreedyAlgorithmTest() throws Exception {
+    public void nongreedyAlgorithmTest() {
         NonGreedyAlgorithm nga = new NonGreedyAlgorithm(prepareNetwork(), 0);
-        Assertions.assertThrows(Exception.class, () -> {
+        Assertions.assertThrows(IllegalStateException.class, () -> {
             nga.findMostFollowersPath("root");
           });
     }
 
     @Test
-    public void nongreedyAlgorithmUnboundedTest() throws Exception {
+    public void nongreedyAlgorithmUnboundedTest() {
         SocialConnector sc = prepareNetwork();
         sc.switchCounter();
         NonGreedyAlgorithm nga = new NonGreedyAlgorithm(sc, 0);

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/minheapmerge/MinHeapUnitTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.algorithms.minheapmerge;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+
+public class MinHeapUnitTest {
+
+    private final int[][] inputArray = { { 0, 6 }, { 1, 5, 10, 100 }, { 2, 4, 200, 650 } };
+    private final int[] expectedArray = { 0, 1, 2, 4, 5, 6, 10, 100, 200, 650 };
+
+    @Test
+    public void givenSortedArrays_whenMerged_thenShouldReturnASingleSortedarray() {
+        int[] resultArray = MinHeap.merge(inputArray);
+        
+        assertThat(resultArray.length, is(equalTo(10)));
+        assertThat(resultArray, is(equalTo(expectedArray)));
+    }
+    
+}

algorithms-sorting-2/.gitignore

@@ -0,0 +1,4 @@
+/target/
+.settings/
+.classpath
+.project

algorithms-sorting-2/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Partitioning and Sorting Arrays with Many Repeated Entries](https://www.baeldung.com/java-sorting-arrays-with-repeated-entries)

algorithms-sorting-2/pom.xml

@@ -0,0 +1,64 @@
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
+         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>
+    <artifactId>algorithms-sorting-2</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>algorithms-sorting-2</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>${commons-math3.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+            <version>${lombok.version}</version>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <version>${junit-jupiter-api.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${org.assertj.core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.codehaus.mojo</groupId>
+                    <artifactId>exec-maven-plugin</artifactId>
+                    <version>${exec-maven-plugin.version}</version>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+
+    <properties>
+        <commons-math3.version>3.6.1</commons-math3.version>
+        <org.assertj.core.version>3.9.0</org.assertj.core.version>
+        <commons-codec.version>1.11</commons-codec.version>
+        <junit-jupiter-api.version>5.3.1</junit-jupiter-api.version>
+    </properties>
+
+</project>

algorithms-sorting-2/src/main/java/com/baeldung/algorithms/quicksort/BentleyMcIlroyPartioning.java

@@ -0,0 +1,66 @@
+package com.baeldung.algorithms.quicksort;
+
+import static com.baeldung.algorithms.quicksort.SortingUtils.swap;
+
+public class BentleyMcIlroyPartioning {
+
+    public static Partition partition(int input[], int begin, int end) {
+        int left = begin, right = end;
+        int leftEqualKeysCount = 0, rightEqualKeysCount = 0;
+
+        int partitioningValue = input[end];
+
+        while (true) {
+            while (input[left] < partitioningValue)
+                left++;
+
+            while (input[right] > partitioningValue) {
+                if (right == begin)
+                    break;
+                right--;
+            }
+
+            if (left == right && input[left] == partitioningValue) {
+                swap(input, begin + leftEqualKeysCount, left);
+                leftEqualKeysCount++;
+                left++;
+            }
+
+            if (left >= right) {
+                break;
+            }
+
+            swap(input, left, right);
+
+            if (input[left] == partitioningValue) {
+                swap(input, begin + leftEqualKeysCount, left);
+                leftEqualKeysCount++;
+            }
+
+            if (input[right] == partitioningValue) {
+                swap(input, right, end - rightEqualKeysCount);
+                rightEqualKeysCount++;
+            }
+            left++; right--;
+        }
+        right = left - 1;
+        for (int k = begin; k < begin + leftEqualKeysCount; k++, right--) {
+            if (right >= begin + leftEqualKeysCount)
+                swap(input, k, right);
+        }
+        for (int k = end; k > end - rightEqualKeysCount; k--, left++) {
+            if (left <= end - rightEqualKeysCount)
+                swap(input, left, k);
+        }
+        return new Partition(right + 1, left - 1);
+    }
+
+    public static void quicksort(int input[], int begin, int end) {
+        if (end <= begin)
+            return;
+        Partition middlePartition = partition(input, begin, end);
+        quicksort(input, begin, middlePartition.getLeft() - 1);
+        quicksort(input, middlePartition.getRight() + 1, end);
+    }
+
+}

algorithms-sorting-2/src/main/java/com/baeldung/algorithms/quicksort/DutchNationalFlagPartioning.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.quicksort;
+
+import static com.baeldung.algorithms.quicksort.SortingUtils.compare;
+import static com.baeldung.algorithms.quicksort.SortingUtils.swap;
+
+public class DutchNationalFlagPartioning {
+
+    public static Partition partition(int[] a, int begin, int end) {
+        int lt = begin, current = begin, gt = end;
+        int partitioningValue = a[begin];
+
+        while (current <= gt) {
+            int compareCurrent = compare(a[current], partitioningValue);
+            switch (compareCurrent) {
+                case -1:
+                    swap(a, current++, lt++);
+                    break;
+                case 0:
+                    current++;
+                    break;
+                case 1:
+                    swap(a, current, gt--);
+                    break;
+            }
+        }
+        return new Partition(lt, gt);
+    }
+
+    public static void quicksort(int[] input, int begin, int end) {
+        if (end <= begin)
+            return;
+
+        Partition middlePartition = partition(input, begin, end);
+
+        quicksort(input, begin, middlePartition.getLeft() - 1);
+        quicksort(input, middlePartition.getRight() + 1, end);
+    }
+}

algorithms-sorting-2/src/main/java/com/baeldung/algorithms/quicksort/Partition.java

@@ -0,0 +1,29 @@
+package com.baeldung.algorithms.quicksort;
+
+public class Partition {
+    private int left;
+    private int right;
+
+    public Partition(int left, int right) {
+        super();
+        this.left = left;
+        this.right = right;
+    }
+
+    public int getLeft() {
+        return left;
+    }
+
+    public void setLeft(int left) {
+        this.left = left;
+    }
+
+    public int getRight() {
+        return right;
+    }
+
+    public void setRight(int right) {
+        this.right = right;
+    }
+
+}

algorithms-sorting-2/src/main/java/com/baeldung/algorithms/quicksort/SortingUtils.java

@@ -0,0 +1,32 @@
+package com.baeldung.algorithms.quicksort;
+
+public class SortingUtils {
+
+    public static void swap(int[] array, int position1, int position2) {
+        if (position1 != position2) {
+            int temp = array[position1];
+            array[position1] = array[position2];
+            array[position2] = temp;
+        }
+    }
+
+    public static int compare(int num1, int num2) {
+        if (num1 > num2)
+            return 1;
+        else if (num1 < num2)
+            return -1;
+        else
+            return 0;
+    }
+
+    public static void printArray(int[] array) {
+        if (array == null) {
+            return;
+        }
+        for (int e : array) {
+            System.out.print(e + " ");
+        }
+        System.out.println();
+    }
+
+}

algorithms-sorting-2/src/main/resources/logback.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT"/>
+    </root>
+</configuration>

algorithms-sorting-2/src/test/java/com/baeldung/algorithms/quicksort/BentleyMcilroyPartitioningUnitTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.algorithms.quicksort;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BentleyMcilroyPartitioningUnitTest {
+
+    @Test
+    public void given_IntegerArray_whenSortedWithBentleyMcilroyPartitioning_thenGetSortedArray() {
+        int[] actual = {3, 2, 2, 2, 3, 7, 7, 3, 2, 2, 7, 3, 3};
+        int[] expected = {2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 7, 7, 7};
+        BentleyMcIlroyPartioning.quicksort(actual, 0, actual.length - 1);
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+}