binary tree implemented

TreeLib.iml

@@ -4,8 +4,19 @@
     <exclude-output />
     <content url="file://$MODULE_DIR$">
       <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/tests" isTestSource="true" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="module-library" scope="TEST">
+      <library name="JUnit4">
+        <CLASSES>
+          <root url="jar://$MAVEN_REPOSITORY$/junit/junit/4.13.1/junit-4.13.1.jar!/" />
+          <root url="jar://$MAVEN_REPOSITORY$/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar!/" />
+        </CLASSES>
+        <JAVADOC />
+        <SOURCES />
+      </library>
+    </orderEntry>
   </component>
 </module>

src/binarytree/BinaryTree.java

@@ -0,0 +1,168 @@
+package binarytree;
+
+import graph.Node;
+import graph.Tree;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * A binary tree is a tree where every node has AT MOST 2 child nodes
+ */
+public class BinaryTree<T extends Comparable<T>> extends Tree<T> {
+
+    public BinaryTree() {
+        this(null);
+    }
+
+    public BinaryTree(T initialValue) {
+        this.root = new BinaryTreeNode<>(null, initialValue); // initialize the root
+    }
+
+    /**
+     * Adds a new node to the tree
+     *
+     * @param value value of the node to be added
+     * @return true if the addition was successful, false otherwise
+     */
+    @Override
+    public Node<T> addNode(T value) {
+        this.values.add(value);
+
+        // if root has not been initialized yet
+        if (this.root.getValue() == null) {
+            this.nodes.add(root);
+
+            this.root.setValue(value);
+
+            return root;
+        }
+
+        // root has been initialized, so call on the root to add the value
+        Node<T> newNode = root.addNode(value);
+
+        this.nodes.add(newNode);
+
+        return newNode;
+    }
+
+    /**
+     * removes a node from the tree, based on value
+     *
+     * @param value the value of the node to be removed
+     * @return true if the node was successfully removed, false otherwise
+     */
+    @Override
+    public boolean removeNode(T value) {
+        if (!this.values.contains(value)) {
+            return false;
+        }
+
+        Node<T> node = findNode(value);
+
+        List<Node<T>> children = new ArrayList<>(node.getChildren());
+
+        // remove the node
+        this.values.remove(value);
+        this.nodes.remove(node);
+
+        if(node.getParent() != null) {
+            node.getParent().getChildren().remove(node);
+            this.nodes.remove(node);
+        } else { // if the value had no parent, it was the root node
+            // set the root node to be the first node of the children list
+            this.root = children.get(0);
+        }
+
+        // binary tree does not put any restrictions on what order the children are in the tree
+        // re-introduce all children into the root
+
+        // it could happen that we have removed the root node and set the first child to be the new root
+        // if so, only reintroduce the other children, omitting the first one
+        int start = 0;
+        if(node.getParent() == null) {
+            start = 1;
+        }
+
+        for (int i = start; i < children.size(); i++) {
+            Node<T> child = children.get(i);
+            this.root.addNode(child.getValue());
+        }
+
+        return true;
+    }
+
+    /**
+     * Removes the passed node
+     *
+     * @param node node to be removed
+     * @return true if the removal was successful, false otherwise
+     */
+    @Override
+    public boolean removeNode(Node<T> node) {
+        if (!this.nodes.contains(node)) {
+            return false;
+        }
+
+        // remove the node
+        this.values.remove(node.getValue());
+        this.nodes.remove(node);
+        node.getParent().getChildren().remove(node);
+
+        // binary tree does not put any restrictions on what order the children are in the tree
+        // re-introduce all children into the parent
+        for (Node<T> child : node.getChildren()) {
+            node.getParent().addNode(child.getValue());
+        }
+
+        return true;
+    }
+
+    /**
+     * Finds the node with passed value
+     *
+     * @param value the value the required node should have
+     * @return the required node if one is present, null otherwise
+     */
+    @Override
+    public Node<T> findNode(T value) {
+        if (!this.values.contains(value)) {
+            return null;
+        }
+
+        // because Binary Tree does not put ANY restrictions on what order the children are in,
+        // we need search through the entire tree
+        // we shall perform a BFS to do this
+        Queue<Node<T>> queue = new ArrayDeque<>();
+        queue.offer(root);
+
+        while (!queue.isEmpty()) {
+            Node<T> current = queue.poll();
+            if (current.getValue().equals(value)) {
+                return current;
+            }
+
+            for (Node<T> child : current.getChildren()) {
+                queue.offer(child);
+            }
+        }
+
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        if(nodes.size() == 0) {
+            return "Empty";
+        }
+
+        StringBuilder sb = new StringBuilder();
+        for(Node<T> n : nodes) {
+            sb.append(n.toString());
+        }
+
+        return sb.toString();
+    }
+}

src/binarytree/BinaryTreeNode.java

@@ -0,0 +1,78 @@
+package binarytree;
+
+import graph.Node;
+
+import java.util.Random;
+
+public class BinaryTreeNode<T extends Comparable<T>> extends Node<T> {
+    public BinaryTreeNode(Node<T> parent, T item) {
+        super(parent, item);
+    }
+
+    /**
+     * Adds a new node to the current node
+     * if the numbers of nodes is larger than 2, proceed to the next node
+     *
+     * @param value value to be added
+     * @return the new node if adding was successful, null otherwise
+     */
+    @Override
+    public Node<T> addNode(T value) {
+        if (children.size() < 2) {
+            Node<T> newChild = new BinaryTreeNode<T>(this, value);
+            this.addNode(newChild);
+
+            return newChild;
+        }
+
+        // pick a random child out of the current children
+        Node<T> randomChild = this.children.get(new Random().nextInt(this.children.size()));
+
+        return randomChild.addNode(value);
+    }
+
+    private void addNode(Node<T> node) {
+        if (children.size() < 2) { // we can still add a node
+            this.children.add(node);
+        } else {
+
+            // pick a random child out of the current children
+            Node<T> randomChild = this.children.get(new Random().nextInt(this.children.size()));
+
+            randomChild.addNode(node.getValue());
+        }
+    }
+
+    @Override
+    public int hashCode() {
+        int randomPrime = 13; // chosen randomly
+
+        int sum = this.children.stream()
+                .map(Node::hashCode)
+                .reduce(0, Integer::sum);
+
+        return (this.value.hashCode() + sum) * randomPrime;
+    }
+
+    @Override
+    public boolean equals(Object that) {
+        if (that instanceof Node<?>) {
+            return ((Node<?>) that).getValue().equals(value);
+        }
+
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(String.format("BT(%s)", value));
+
+        for(Node<T> child : children) {
+            sb.append(":");
+            sb.append(child.toString());
+        }
+
+        return sb.toString();
+    }
+}

src/graph/Graph.java

@@ -1,11 +0,0 @@
-package graph;
-
-import java.util.List;
-
-public abstract class Graph {
-    protected List<Node> nodes;
-
-    public List<Node> getAllNodes() {
-        return nodes;
-    }
-}

src/graph/Node.java

@@ -1,20 +1,46 @@
 package graph;
 
+import java.util.ArrayList;
 import java.util.List;
 
-public abstract class Node {
+public abstract class Node<T extends Comparable<T>> {
-    private final String item;
+    protected T value;
-    private List<Node> children;
+    protected Node<T> parent;
+    protected final List<Node<T>> children;
 
-    public Node(String item) {
+    public Node(Node<T> parent, T value) {
-        this.item = item;
+        this.value = value;
+        this.parent = parent;
+        this.children = new ArrayList<>();
     }
 
-    public String getItem() {
+    public T getValue() {
-        return item;
+        return value;
     }
 
-    public List<Node> getChildren() {
+    public void setValue(T value) {
+        this.value = value;
+    }
+
+    public List<Node<T>> getChildren() {
         return children;
     }
+
+    public Node<T> getParent() {
+        return parent;
+    }
+
+    public abstract Node<T> addNode(T value);
+
+    @Override
+    public int hashCode() {
+        return value.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        return super.equals(obj);
+    }
+
+    public abstract String toString();
 }

src/graph/Tree.java

@@ -0,0 +1,35 @@
+package graph;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+public abstract class Tree<T extends Comparable<T>> {
+    protected Node<T> root;
+    protected List<Node<T>> nodes;
+    protected Set<T> values;
+
+    public Tree() {
+        this.nodes = new ArrayList<>();
+        this.values = new HashSet<>();
+    }
+
+    public List<Node<T>> getAllNodes() {
+        return nodes;
+    }
+
+    public int getSize() {
+        return nodes.size();
+    }
+
+    public Node<T> getRoot() {
+        return root;
+    }
+
+    public abstract Node<T> addNode(T value);
+    public abstract boolean removeNode(T value);
+    public abstract boolean removeNode (Node<T> n);
+    public abstract Node<T> findNode(T value);
+    public abstract String toString();
+}

tests/BinaryTreeTests.java

@@ -0,0 +1,55 @@
+import binarytree.BinaryTree;
+import binarytree.BinaryTreeNode;
+import graph.Node;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+public class BinaryTreeTests {
+    BinaryTree<Integer> tree;
+
+    @Before
+    public void init() {
+        this.tree = new BinaryTree<>();
+    }
+
+    @Test
+    public void testAddition() {
+        Node<Integer> n1 = tree.addNode(1);
+        Node<Integer> n2 = tree.addNode(2);
+
+        Assert.assertEquals(2, tree.getSize());
+        Assert.assertEquals(n1, tree.findNode(1));
+        Assert.assertEquals(n2, tree.findNode(2));
+        Assert.assertNull(tree.findNode(3));
+        Assert.assertEquals(1, tree.getRoot().getValue().intValue());
+        Assert.assertEquals(2, tree.getRoot().getChildren().get(0).getValue().intValue());
+    }
+
+    @Test
+    public void testAddition2() {
+        tree.addNode(1);
+        tree.addNode(2);
+        tree.addNode(3);
+        tree.addNode(4);
+
+        Assert.assertEquals(4, tree.getSize());
+    }
+
+    @Test
+    public void testAddition3() {
+        Node<Integer> n1 = new BinaryTreeNode<>(null, 1);
+    }
+
+    @Test
+    public void testRemoval() {
+        tree.addNode(1);
+        tree.addNode(2);
+        System.out.println(tree);
+
+        tree.removeNode(1);
+        System.out.println(tree);
+        Assert.assertEquals(1, tree.getSize());
+        Assert.assertEquals(2, tree.getRoot().getValue().intValue());
+    }
+}