JAVA-12097: renamed algorithms-module to algorithms-modules

2022-05-20 22:07:32 +05:30
parent 2d7de1343f
commit 93b93417e0
324 changed files with 31 additions and 20 deletions
@@ -0,0 +1,33 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+public class BalancedBinaryTree {
+
+    public static boolean isBalanced(Tree tree) {
+        return isBalancedRecursive(tree, -1).isBalanced;
+    }
+
+    private static Result isBalancedRecursive(Tree tree, int depth) {
+        if (tree == null) {
+            return new Result(true, -1);
+        }
+
+        Result leftSubtreeResult = isBalancedRecursive(tree.left(), depth + 1);
+        Result rightSubtreeResult = isBalancedRecursive(tree.right(), depth + 1);
+
+        boolean isBalanced = Math.abs(leftSubtreeResult.height - rightSubtreeResult.height) <= 1;
+        boolean subtreesAreBalanced = leftSubtreeResult.isBalanced && rightSubtreeResult.isBalanced;
+        int height = Math.max(leftSubtreeResult.height, rightSubtreeResult.height) + 1;
+
+        return new Result(isBalanced && subtreesAreBalanced, height);
+    }
+
+    private static final class Result {
+        private final boolean isBalanced;
+        private final int height;
+
+        private Result(boolean isBalanced, int height) {
+            this.isBalanced = isBalanced;
+            this.height = height;
+        }
+    }
+}
@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.balancedbinarytree;
+
+public class Tree {
+    private final int value;
+    private final Tree left;
+    private final Tree right;
+
+    public Tree(int value, Tree left, Tree right) {
+        this.value = value;
+        this.left = left;
+        this.right = right;
+    }
+
+    public int value() {
+        return value;
+    }
+
+    public Tree left() {
+        return left;
+    }
+
+    public Tree right() {
+        return right;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("[%s, %s, %s]",
+            value,
+            left == null ? "null" : left.toString(),
+            right == null ? "null" : right.toString()
+        );
+    }
+}
@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.binarygap;
+
+public class BinaryGap {
+    static int calculateBinaryGap(int n) {
+        return calculateBinaryGap(n >>> Integer.numberOfTrailingZeros(n), 0, 0);
+    }
+
+    static int calculateBinaryGap(int n, int current, int maximum) {
+        if (n == 0) {
+            return maximum;
+        } else if ((n & 1) == 0) {
+            return calculateBinaryGap(n >>> 1, current + 1, maximum);
+        } else {
+            return calculateBinaryGap(n >>> 1, 0, Math.max(maximum, current));
+        }
+    }
+}
@@ -0,0 +1,67 @@
+package com.baeldung.algorithms.combinatorics;
+
+import java.util.*;
+
+import static java.util.Collections.swap;
+
+public class Combinatorics {
+
+    public static List<List<Integer>> permutations(List<Integer> sequence) {
+        List<List<Integer>> results = new ArrayList<>();
+        permutationsInternal(sequence, results, 0);
+        return results;
+    }
+
+    private static void permutationsInternal(List<Integer> sequence, List<List<Integer>> results, int index) {
+        if (index == sequence.size() - 1) {
+            results.add(new ArrayList<>(sequence));
+        }
+
+        for (int i = index; i < sequence.size(); i++) {
+            swap(sequence, i, index);
+            permutationsInternal(sequence, results, index + 1);
+            swap(sequence, i, index);
+        }
+    }
+
+    public static List<List<Integer>> combinations(List<Integer> inputSet, int k) {
+        List<List<Integer>> results = new ArrayList<>();
+        combinationsInternal(inputSet, k, results, new ArrayList<>(), 0);
+        return results;
+    }
+
+    private static void combinationsInternal(
+      List<Integer> inputSet, int k, List<List<Integer>> results, ArrayList<Integer> accumulator, int index) {
+        int leftToAccumulate = k - accumulator.size();
+        int possibleToAcculumate = inputSet.size() - index;
+
+        if (accumulator.size() == k) {
+            results.add(new ArrayList<>(accumulator));
+        } else if (leftToAccumulate <= possibleToAcculumate) {
+            combinationsInternal(inputSet, k, results, accumulator, index + 1);
+
+            accumulator.add(inputSet.get(index));
+            combinationsInternal(inputSet, k, results, accumulator, index + 1);
+            accumulator.remove(accumulator.size() - 1);
+        }
+    }
+
+    public static List<List<Character>> powerSet(List<Character> sequence) {
+        List<List<Character>> results = new ArrayList<>();
+        powerSetInternal(sequence, results, new ArrayList<>(), 0);
+        return results;
+    }
+
+    private static void powerSetInternal(
+      List<Character> set, List<List<Character>> powerSet, List<Character> accumulator, int index) {
+        if (index == set.size()) {
+            powerSet.add(new ArrayList<>(accumulator));
+        } else {
+            accumulator.add(set.get(index));
+
+            powerSetInternal(set, powerSet, accumulator, index + 1);
+            accumulator.remove(accumulator.size() - 1);
+            powerSetInternal(set, powerSet, accumulator, index + 1);
+        }
+    }
+}
@@ -0,0 +1,110 @@
+package com.baeldung.algorithms.conversion;
+
+import java.math.BigInteger;
+
+import javax.xml.bind.DatatypeConverter;
+
+import org.apache.commons.codec.DecoderException;
+import org.apache.commons.codec.binary.Hex;
+
+import com.google.common.io.BaseEncoding;
+
+public class HexStringConverter {
+
+    /**
+     * Create a byte Array from String of hexadecimal digits using Character conversion 
+     * @param hexString - Hexadecimal digits as String
+     * @return Desired byte Array
+     */
+    public byte[] decodeHexString(String hexString) {
+        if (hexString.length() % 2 == 1) {
+            throw new IllegalArgumentException("Invalid hexadecimal String supplied.");
+        }
+        byte[] bytes = new byte[hexString.length() / 2];
+
+        for (int i = 0; i < hexString.length(); i += 2) {
+            bytes[i / 2] = hexToByte(hexString.substring(i, i + 2));
+        }
+        return bytes;
+    }
+
+    /**
+     * Create a String of hexadecimal digits from a byte Array using Character conversion
+     * @param byteArray - The byte Array
+     * @return Desired String of hexadecimal digits in lower case
+     */
+    public String encodeHexString(byte[] byteArray) {
+        StringBuffer hexStringBuffer = new StringBuffer();
+        for (int i = 0; i < byteArray.length; i++) {
+            hexStringBuffer.append(byteToHex(byteArray[i]));
+        }
+        return hexStringBuffer.toString();
+    }
+
+    public String byteToHex(byte num) {
+        char[] hexDigits = new char[2];
+        hexDigits[0] = Character.forDigit((num >> 4) & 0xF, 16);
+        hexDigits[1] = Character.forDigit((num & 0xF), 16);
+        return new String(hexDigits);
+    }
+
+    public byte hexToByte(String hexString) {
+        int firstDigit = toDigit(hexString.charAt(0));
+        int secondDigit = toDigit(hexString.charAt(1));
+        return (byte) ((firstDigit << 4) + secondDigit);
+    }
+
+    private int toDigit(char hexChar) {
+        int digit = Character.digit(hexChar, 16);
+        if(digit == -1) {
+            throw new IllegalArgumentException("Invalid Hexadecimal Character: "+ hexChar);
+        }
+        return digit;
+    }
+
+    public String encodeUsingBigIntegerToString(byte[] bytes) {
+        BigInteger bigInteger = new BigInteger(1, bytes);
+        return bigInteger.toString(16);
+    }
+
+    public String encodeUsingBigIntegerStringFormat(byte[] bytes) {
+        BigInteger bigInteger = new BigInteger(1, bytes);
+        return String.format("%0" + (bytes.length << 1) + "x", bigInteger);
+    }
+
+    public byte[] decodeUsingBigInteger(String hexString) {
+        byte[] byteArray = new BigInteger(hexString, 16).toByteArray();
+        if (byteArray[0] == 0) {
+            byte[] output = new byte[byteArray.length - 1];
+            System.arraycopy(byteArray, 1, output, 0, output.length);
+            return output;
+        }
+        return byteArray;
+    }
+
+    public String encodeUsingDataTypeConverter(byte[] bytes) {
+        return DatatypeConverter.printHexBinary(bytes);
+    }
+
+    public byte[] decodeUsingDataTypeConverter(String hexString) {
+        return DatatypeConverter.parseHexBinary(hexString);
+    }
+
+    public String encodeUsingApacheCommons(byte[] bytes) throws DecoderException {
+        return Hex.encodeHexString(bytes);
+    }
+
+    public byte[] decodeUsingApacheCommons(String hexString) throws DecoderException {
+        return Hex.decodeHex(hexString);
+    }
+
+    public String encodeUsingGuava(byte[] bytes) {
+        return BaseEncoding.base16()
+            .encode(bytes);
+    }
+
+    public byte[] decodeUsingGuava(String hexString) {
+        return BaseEncoding.base16()
+            .decode(hexString.toUpperCase());
+    }
+}
@@ -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 +1,36 @@
+package com.baeldung.algorithms.knapsack;
+
+public class Knapsack {
+
+    public int knapsackRec(int[] w, int[] v, int n, int W) {
+        if (n <= 0) {
+            return 0;
+        } else if (w[n - 1] > W) {
+            return knapsackRec(w, v, n - 1, W);
+        } else {
+            return Math.max(knapsackRec(w, v, n - 1, W), v[n - 1] + knapsackRec(w, v, n - 1, W - w[n - 1]));
+        }
+    }
+
+    public int knapsackDP(int[] w, int[] v, int n, int W) {
+        if (n <= 0 || W <= 0) {
+            return 0;
+        }
+
+        int[][] m = new int[n + 1][W + 1];
+        for (int j = 0; j <= W; j++) {
+            m[0][j] = 0;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= W; j++) {
+                if (w[i - 1] > j) {
+                    m[i][j] = m[i - 1][j];
+                } else {
+                    m[i][j] = Math.max(m[i - 1][j], m[i - 1][j - w[i - 1]] + v[i - 1]);
+                }
+            }
+        }
+        return m[n][W];
+    }
+}
@@ -0,0 +1,35 @@
+package com.baeldung.algorithms.maximumsubarray;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class BruteForceAlgorithm {
+
+    private Logger logger = LoggerFactory.getLogger(BruteForceAlgorithm.class.getName());
+
+    public int maxSubArray(int[] arr) {
+
+        int size = arr.length;
+        int maximumSubArraySum = Integer.MIN_VALUE;
+        int start = 0;
+        int end = 0;
+
+        for (int left = 0; left < size; left++) {
+
+            int runningWindowSum = 0;
+
+            for (int right = left; right < size; right++) {
+                runningWindowSum += arr[right];
+
+                if (runningWindowSum > maximumSubArraySum) {
+                    maximumSubArraySum = runningWindowSum;
+                    start = left;
+                    end = right;
+                }
+            }
+        }
+        logger.info("Found Maximum Subarray between {} and {}", start, end);
+        return maximumSubArraySum;
+    }
+
+}
@@ -0,0 +1,34 @@
+package com.baeldung.algorithms.maximumsubarray;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class KadaneAlgorithm {
+
+    private Logger logger = LoggerFactory.getLogger(BruteForceAlgorithm.class.getName());
+
+    public int maxSubArraySum(int[] arr) {
+
+        int size = arr.length;
+        int start = 0;
+        int end = 0;
+
+        int maxSoFar = arr[0], maxEndingHere = arr[0];
+        for (int i = 0; i < size; i++) {
+
+            if (arr[i] > maxEndingHere + arr[i]) {
+                start = i;
+                maxEndingHere = arr[i];
+            } else {
+                maxEndingHere = maxEndingHere + arr[i];
+            }
+
+            if (maxSoFar < maxEndingHere) {
+                maxSoFar = maxEndingHere;
+                end = i;
+            }
+        }
+        logger.info("Found Maximum Subarray between {} and {}", Math.min(start, end), end);
+        return maxSoFar;
+    }
+}
@@ -0,0 +1,33 @@
+package com.baeldung.algorithms.mergesortedarrays;
+
+public class SortedArrays {
+
+    public static int[] merge(int[] foo, int[] bar) {
+
+        int fooLength = foo.length;
+        int barLength = bar.length;
+
+        int[] merged = new int[fooLength + barLength];
+
+        int fooPosition, barPosition, mergedPosition;
+        fooPosition = barPosition = mergedPosition = 0;
+
+        while (fooPosition < fooLength && barPosition < barLength) {
+            if (foo[fooPosition] < bar[barPosition]) {
+                merged[mergedPosition++] = foo[fooPosition++];
+            } else {
+                merged[mergedPosition++] = bar[barPosition++];
+            }
+        }
+
+        while (fooPosition < fooLength) {
+            merged[mergedPosition++] = foo[fooPosition++];
+        }
+
+        while (barPosition < barLength) {
+            merged[mergedPosition++] = bar[barPosition++];
+        }
+
+        return merged;
+    }
+}
@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.prim;
+
+public class Edge {
+
+    private int weight;
+    private boolean isIncluded = false;
+    private boolean isPrinted = false;
+
+    public Edge(int weight) {
+        this.weight = weight;
+    }
+
+    public int getWeight() {
+        return weight;
+    }
+
+    public void setWeight(int weight) {
+        this.weight = weight;
+    }
+
+    public boolean isIncluded() {
+        return isIncluded;
+    }
+
+    public void setIncluded(boolean included) {
+        isIncluded = included;
+    }
+
+    public boolean isPrinted() {
+        return isPrinted;
+    }
+
+    public void setPrinted(boolean printed) {
+        isPrinted = printed;
+    }
+}
@@ -0,0 +1,73 @@
+package com.baeldung.algorithms.prim;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.math3.util.Pair;
+
+public class Prim {
+
+    private List<Vertex> graph;
+
+    public Prim(List<Vertex> graph){
+        this.graph = graph;
+    }
+
+    public void run(){
+        if (graph.size() > 0){
+            graph.get(0).setVisited(true);
+        }
+        while (isDisconnected()){
+            Edge nextMinimum = new Edge(Integer.MAX_VALUE);
+            Vertex nextVertex = graph.get(0);
+            for (Vertex vertex : graph){
+                if (vertex.isVisited()){
+                    Pair<Vertex, Edge> candidate = vertex.nextMinimum();
+                    if (candidate.getValue().getWeight() < nextMinimum.getWeight()){
+                        nextMinimum = candidate.getValue();
+                        nextVertex = candidate.getKey();
+                    }
+                }
+            }
+            nextMinimum.setIncluded(true);
+            nextVertex.setVisited(true);
+        }
+    }
+
+    private boolean isDisconnected(){
+        for (Vertex vertex : graph){
+            if (!vertex.isVisited()){
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public String originalGraphToString(){
+        StringBuilder sb = new StringBuilder();
+        for (Vertex vertex : graph){
+            sb.append(vertex.originalToString());
+        }
+        return sb.toString();
+    }
+
+    public void resetPrintHistory(){
+        for (Vertex vertex : graph){
+            Iterator<Map.Entry<Vertex,Edge>> it = vertex.getEdges().entrySet().iterator();
+            while (it.hasNext()) {
+                Map.Entry<Vertex,Edge> pair = it.next();
+                pair.getValue().setPrinted(false);
+            }
+        }
+    }
+
+    public String minimumSpanningTreeToString(){
+        StringBuilder sb = new StringBuilder();
+        for (Vertex vertex : graph){
+            sb.append(vertex.includedToString());
+        }
+        return sb.toString();
+    }
+
+}
@@ -0,0 +1,106 @@
+package com.baeldung.algorithms.prim;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+import org.apache.commons.math3.util.Pair;
+
+public class Vertex {
+
+    private String label = null;
+    private Map<Vertex, Edge> edges = new HashMap<>();
+    private boolean isVisited = false;
+
+    public Vertex(String label){
+        this.label = label;
+    }
+
+    public String getLabel() {
+        return label;
+    }
+
+    public void setLabel(String label) {
+        this.label = label;
+    }
+
+    public Map<Vertex, Edge> getEdges() {
+        return edges;
+    }
+
+    public void addEdge(Vertex vertex, Edge edge){
+        if (this.edges.containsKey(vertex)){
+            if (edge.getWeight() < this.edges.get(vertex).getWeight()){
+                this.edges.replace(vertex, edge);
+            }
+        } else {
+            this.edges.put(vertex, edge);
+        }
+    }
+
+    public boolean isVisited() {
+        return isVisited;
+    }
+
+    public void setVisited(boolean visited) {
+        isVisited = visited;
+    }
+
+    public Pair<Vertex, Edge> nextMinimum(){
+        Edge nextMinimum = new Edge(Integer.MAX_VALUE);
+        Vertex nextVertex = this;
+        Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Vertex,Edge> pair = it.next();
+            if (!pair.getKey().isVisited()){
+                if (!pair.getValue().isIncluded()) {
+                    if (pair.getValue().getWeight() < nextMinimum.getWeight()) {
+                        nextMinimum = pair.getValue();
+                        nextVertex = pair.getKey();
+                    }
+                }
+            }
+        }
+        return new Pair<>(nextVertex, nextMinimum);
+    }
+
+    public String originalToString(){
+        StringBuilder sb = new StringBuilder();
+        Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Vertex,Edge> pair = it.next();
+            if (!pair.getValue().isPrinted()) {
+                sb.append(getLabel());
+                sb.append(" --- ");
+                sb.append(pair.getValue().getWeight());
+                sb.append(" --- ");
+                sb.append(pair.getKey().getLabel());
+                sb.append("\n");
+                pair.getValue().setPrinted(true);
+            }
+        }
+        return sb.toString();
+    }
+
+    public String includedToString(){
+        StringBuilder sb = new StringBuilder();
+        if (isVisited()) {
+            Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+            while (it.hasNext()) {
+                Map.Entry<Vertex,Edge> pair = it.next();
+                if (pair.getValue().isIncluded()) {
+                    if (!pair.getValue().isPrinted()) {
+                        sb.append(getLabel());
+                        sb.append(" --- ");
+                        sb.append(pair.getValue().getWeight());
+                        sb.append(" --- ");
+                        sb.append(pair.getKey().getLabel());
+                        sb.append("\n");
+                        pair.getValue().setPrinted(true);
+                    }
+                }
+            }
+        }
+        return sb.toString();
+    }
+}
@@ -0,0 +1,45 @@
+package com.baeldung.algorithms.relativelyprime;
+
+import java.math.BigInteger;
+
+class RelativelyPrime {
+
+    static boolean iterativeRelativelyPrime(int a, int b) {
+        return iterativeGCD(a, b) == 1;
+    }
+
+    static boolean recursiveRelativelyPrime(int a, int b) {
+        return recursiveGCD(a, b) == 1;
+    }
+
+    static boolean bigIntegerRelativelyPrime(int a, int b) {
+        return BigInteger.valueOf(a).gcd(BigInteger.valueOf(b)).equals(BigInteger.ONE);
+    }
+
+    private static int iterativeGCD(int a, int b) {
+        int tmp;
+        while (b != 0) {
+            if (a < b) {
+                tmp = a;
+                a = b;
+                b = tmp;
+            }
+            tmp = b;
+            b = a % b;
+            a = tmp;
+        }
+        return a;
+    }
+
+    private static int recursiveGCD(int a, int b) {
+        if (b == 0) {
+            return a;
+        }
+        if (a < b) {
+            return recursiveGCD(b, a);
+        }
+        return recursiveGCD(b, a % b);
+    }
+
+
+}
@@ -0,0 +1,42 @@
+package com.baeldung.algorithms.reversingtree;
+
+public class TreeNode {
+
+    private int value;
+    private TreeNode rightChild;
+    private TreeNode leftChild;
+
+    public int getValue() {
+        return value;
+    }
+
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    public TreeNode getRightChild() {
+        return rightChild;
+    }
+
+    public void setRightChild(TreeNode rightChild) {
+        this.rightChild = rightChild;
+    }
+
+    public TreeNode getLeftChild() {
+        return leftChild;
+    }
+
+    public void setLeftChild(TreeNode leftChild) {
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value, TreeNode leftChild, TreeNode rightChild) {
+        this.value = value;
+        this.rightChild = rightChild;
+        this.leftChild = leftChild;
+    }
+
+    public TreeNode(int value) {
+        this.value = value;
+    }
+}
@@ -0,0 +1,53 @@
+package com.baeldung.algorithms.reversingtree;
+
+import java.util.LinkedList;
+
+public class TreeReverser {
+
+    public void reverseRecursive(TreeNode treeNode) {
+        if (treeNode == null) {
+            return;
+        }
+
+        TreeNode temp = treeNode.getLeftChild();
+        treeNode.setLeftChild(treeNode.getRightChild());
+        treeNode.setRightChild(temp);
+
+        reverseRecursive(treeNode.getLeftChild());
+        reverseRecursive(treeNode.getRightChild());
+    }
+
+    public void reverseIterative(TreeNode treeNode) {
+        LinkedList<TreeNode> queue = new LinkedList<TreeNode>();
+
+        if (treeNode != null) {
+            queue.add(treeNode);
+        }
+
+        while (!queue.isEmpty()) {
+
+            TreeNode node = queue.poll();
+            if (node.getLeftChild() != null)
+                queue.add(node.getLeftChild());
+            if (node.getRightChild() != null)
+                queue.add(node.getRightChild());
+
+            TreeNode temp = node.getLeftChild();
+            node.setLeftChild(node.getRightChild());
+            node.setRightChild(temp);
+        }
+    }
+
+    public String toString(TreeNode root) {
+        if (root == null) {
+            return "";
+        }
+
+        StringBuffer buffer = new StringBuffer(String.valueOf(root.getValue())).append(" ");
+
+        buffer.append(toString(root.getLeftChild()));
+        buffer.append(toString(root.getRightChild()));
+
+        return buffer.toString();
+    }
+}
@@ -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>