AlgoDat/TerryModi/RBTree.java

import java.io.FileWriter;
import java.io.IOException;
//
class RBTree<T extends Comparable<T>> {

    private static final boolean RED = true;
    private static final boolean BLACK = false;

    private class Node {
        T key; // Node<Integer>, generischer Datentyp, der Schlüssel (key) des Knotens vom Typ Integer ist.
        Node left, right, parent; // Elternknoten hinzugefügt
        boolean color;

        public Node(T key) { // Konstruktor von Node-Class
            this.key = key;
            left = right = parent = null;
            this.color = true; // Neue Knoten sind standardmäßig rot
        }
    }

    private Node root;


    public void insertNode(T key) { // hier nicht int-DT, sondern T,
        // mit jedem vergleichbaren Datentyp (T)
        // verwendet werden kann, solange dieser das Comparable-Interface implementiert.

        Node node = root;
        Node parent = null;

        // Traverse the tree to the left or right depending on the key,
        // finding a correct position for the insertion of nodes later + keep the structure of the tree
        while (node != null) {
            parent = node;
            if (key.compareTo(node.key) < 0) { // key < node.key
                node = node.left;
            } else if (key.compareTo(node.key) > 0) { // key > node.key
                node = node.right;
            } else {
                throw new IllegalArgumentException("BST already contains a node with key " + key);
            }
        }

        // Insert new node
        Node newNode = new Node(key);
        newNode.color = true; // neuer Knoten immer rot
        if (parent == null) {
            root = newNode;
        } else if (key.compareTo(parent.key) < 0) { // key < parent.key
            parent.left = newNode;
        } else if (key.compareTo(parent.key) > 0){ // key > parent.key
            parent.right = newNode;
        }
        newNode.parent = parent; // etablieren die Verbindung des Knotens zu seinem Vater
        fixAfterInsert(newNode);
    }

    private Node getUncle(Node parent) { // für spätere Implementierung fix()
        Node grandparent = parent.parent;

        if (grandparent.left == parent) {
            return grandparent.right; // right is the uncle

        } else if (grandparent.right == parent) {
            return grandparent.left; // left is the uncle

        } else {
            throw new IllegalStateException("Parent is not a child of its grandparent");
        }
    }

    private void fixAfterInsert(Node node) {
        Node parent = node.parent;

        // Case 1: no root, add node as new root, root is always black
        if (parent == null) {
            node.color = false;
            return;
        }

        // Parent is black --> nothing to do
        if (parent.color == false) { // Abbildung S.312, aber beide Knoten sind schon schwarz gefärbt
            return;
        }

        // From here on, parent(vater) is red
        Node grandparent = parent.parent;

        Node uncle = getUncle(parent); // Get the uncle (maybe nil, in which case its color is BLACK)

        // Case 3 (parent uncle red, Abbildung S.313, 314): recolor parent, grandparent
        // and uncle
        if (uncle != null && uncle.color == true) {
            parent.color = false;
            uncle.color = false;
            grandparent.color = true;

            // Call recursively for grandparent, which is now red. fix recursively
            fixAfterInsert(grandparent);
        }

        // Parent is left child of grandparent
        // Case 4a: Uncle is black(nil is default black) and node is left --> right
        // "inner child" of its grandparent
        else if (parent == grandparent.left) {

            if (node == parent.right) {
                rotateLeft(parent);

                // Let "parent" point to the new root node of the rotated sub-tree.
                // It will be recolored in the next step, which we're going to fall-through to.
                parent = node;
            }

            // Case 5a: Uncle is black and node is left->left "outer child" of its grandparent
            rotateRight(grandparent);

            // Recolor original parent and grandparent
            parent.color = false;
            grandparent.color = true;
        }

        // Parent is right child of grandparent
        else if (parent == grandparent.right) {
            // Case 4b: Uncle is black and node is right->left "inner child" of its
            // grandparent
            if (node == parent.left) {
                rotateRight(parent);

                // Let "parent" point to the new root node of the rotated sub-tree.
                // It will be recolored in the next step, which we're going to fall-through to.
                parent = node;
            }

            // Case 5b: Uncle is black and node is right->right "outer child" of its
            // grandparent
            rotateLeft(grandparent);

            // Recolor original parent and grandparent
            parent.color = false;
            grandparent.color = true;
        }
    }

    private Node rotateLeft(Node node) {
        Node rightChild = node.right;
        Node parent = node.parent;

        node.right = rightChild.left;
        if (rightChild.left != null) {
            rightChild.left.parent = node;
        }

        rightChild.left = node;
        node.parent = rightChild;

        rightChild.parent = parent;
        if (parent == null) {
            root = rightChild;
        } else if (node == parent.left) {
            parent.left = rightChild;
        } else if (node == parent.right) {
            parent.right = rightChild;
        } else {
            throw new IllegalStateException("Node is not a child of its parent");
        }


        RootBlack();

        return rightChild;
    }

    private Node rotateRight(Node node) {
        Node leftChild = node.left;
        Node parent = node.parent;

        node.left = leftChild.right;
        if (leftChild.right != null) {
            leftChild.right.parent = node;
        }

        leftChild.right = node;
        node.parent = leftChild;

        leftChild.parent = parent;
        if (parent == null) {
            root = leftChild;
        } else if (node == parent.left) {
            parent.left = leftChild;
        } else if (node == parent.right) {
            parent.right = leftChild;
        } else {
            throw new IllegalStateException("Node is not a child of its parent");
        }

        RootBlack();

        return leftChild;
    }

    /* private void flipColors(Node node) {
        node.color = !node.color;
        node.left.color = !node.left.color;
        node.right.color = !node.right.color;
    } */

    private void RootBlack() {
        root.color = BLACK;
    }

    /*
     * public void printDOTAfterInsert(String filename, T key) {
     * try (FileWriter writer = new FileWriter(filename)) {
     * writer.write("digraph G {\n");
     * writer.write("\tnode [style=filled, color=black, shape=circle, width=.6,\n");
     * writer.write("\t\tfontname=Helvetica, fontweight=bold, fontcolor=white,\n");
     * writer.write("\t\tfontsize=24, fixedsize=true];\n");
     *
     * root = insert(root, null, key); // Füge das Element ein und aktualisiere den
     * Baum
     * printDOTRecursive(root, writer);
     *
     * writer.write("}\n");
     * } catch (IOException e) {
     * e.printStackTrace();
     * }
     * }
     */

    public void printDOTAfterInsert(String filename) {

        try (FileWriter writer = new FileWriter(filename)) {
            writer.write("digraph G {\n");
            writer.write("\tnode [style=filled, color=black, shape=circle, width=.6,\n");
            writer.write("\t\tfontname=Helvetica, fontweight=bold, fontcolor=white,\n");
            writer.write("\t\tfontsize=24, fixedsize=true];\n");

            // Hier wird der gesamte Baum gezeichnet, nicht nur der neu eingefügte Schlüssel
            printDOTRecursive(root, writer);

            writer.write("}\n");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void printDOTRecursive(Node node, FileWriter writer) throws IOException {
        if (node != null) {
            String keyString = node.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
            String fillColor = (node.color == RED) ? "red" : "black";
            String fontColor = (node.color == RED) ? "white" : "white";

            writer.write("\t\"" + keyString + "\" [fillcolor=" + fillColor + ", fontcolor=" + fontColor + "];\n");

            // Print parent link
           /*  if (node.parent != null) {
                String parentKeyString = node.parent.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
                writer.write("\t\"" + parentKeyString + "\" -> \"" + keyString + "\" [style=dotted];\n");
            } */

            // Print left child
            if (node.left != null) {
                String leftKeyString = node.left.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
                writer.write("\t\"" + keyString + "\" -> \"" + leftKeyString + "\";\n");
                printDOTRecursive(node.left, writer);
            } else {
                String leftNilKeyString = keyString + "_NIL_L";
                writer.write("\t\"" + leftNilKeyString + "\" [shape=plaintext, label=\"NIL\", fontsize=16];\n");
                writer.write("\t\"" + keyString + "\" -> \"" + leftNilKeyString + "\";\n");
            }

            // Print right child
            if (node.right != null) {
                String rightKeyString = node.right.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
                writer.write("\t\"" + keyString + "\" -> \"" + rightKeyString + "\";\n");
                printDOTRecursive(node.right, writer);
            } else {
                String rightNilKeyString = keyString + "_NIL_R";
                writer.write("\t\"" + rightNilKeyString + "\" [shape=plaintext, label=\"NIL\", fontsize=16];\n");
                writer.write("\t\"" + keyString + "\" -> \"" + rightNilKeyString + "\";\n");
            }
        }
    }


    /*public void printDOTAfterInsert(String filename, T key) {
        try (FileWriter writer = new FileWriter(filename)) {
            writer.write("digraph G {\n");
            writer.write("\tnode [style=filled, color=black, shape=circle, width=.6,\n");
            writer.write("\t\tfontname=Helvetica, fontweight=bold, fontcolor=white,\n");
            writer.write("\t\tfontsize=24, fixedsize=true];\n");

            // Hier wird der gesamte Baum gezeichnet, nicht nur der neu eingefügte Schlüssel
            printDOTRecursive(root, writer);

            writer.write("}\n");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void printDOTRecursive(Node node, FileWriter writer) throws IOException {
        if (node != null) {
            String keyString = node.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
            String fillColor = (node.color == RED) ? "red" : "black";
            String fontColor = (node.color == RED) ? "white" : "white";

            writer.write("\t\"" + keyString + "\" [fillcolor=" + fillColor + ", fontcolor=" + fontColor + "];\n");

            /*
             * Print parent link
             * if (node.parent != null) {
             * String parentKeyString =
             * node.parent.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
             * writer.write("\t\"" + parentKeyString + "\" -> \"" + keyString +
             * "\" [style=dotted];\n");
             * }


            // Print left child
            if (node.left != null) {
                String leftKeyString = node.left.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
                writer.write("\t\"" + keyString + "\" -> \"" + leftKeyString + "\";\n");
                printDOTRecursive(node.left, writer);
            } else {
                String leftNilKeyString = keyString + "_NIL_L";
                writer.write("\t\"" + leftNilKeyString + "\" [shape=plaintext, label=\"NIL\", fontsize=16];\n");
                writer.write("\t\"" + keyString + "\" -> \"" + leftNilKeyString + "\";\n");
            }

            // Print right child
            if (node.right != null) {
                String rightKeyString = node.right.key.toString().replaceAll("[^a-zA-Z0-9]", "_");
                writer.write("\t\"" + keyString + "\" -> \"" + rightKeyString + "\";\n");
                printDOTRecursive(node.right, writer);
            } else {
                String rightNilKeyString = keyString + "_NIL_R";
                writer.write("\t\"" + rightNilKeyString + "\" [shape=plaintext, label=\"NIL\", fontsize=16];\n");
                writer.write("\t\"" + keyString + "\" -> \"" + rightNilKeyString + "\";\n");
            }
        }
    */
}