public static int[][] chunk(int[] numbers, int size) {
    return IntStream.iterate(0, i -> i + size)
            .limit((long) Math.ceil((double) numbers.length / size))
            .mapToObj(cur -> Arrays.copyOfRange(numbers, cur, Math.min(cur + size, numbers.length)))
            .toArray(int[][]::new);
}

public static <T> T[] concat(T[] first, T[] second) {
    return Stream.concat(Stream.of(first), Stream.of(second))
            .toArray(i -> (T[]) Arrays.copyOf(new Object[0], i, first.getClass()));
}

public static long countOccurrences(int[] numbers, int value) {
    return Arrays.stream(numbers)
            .filter(e -> e == value)
            .count();
}

public static int[] deepFlatten(Object[] elements) {
    return Arrays.stream(elements)
            .flatMapToInt(e -> {
              if (e instanceof Object[]) {
                  return Arrays.stream(deepFlatten(((Object[]) e)));
              }
              return IntStream.of((Integer) e);
            }).toArray();
}

public static int[] difference(int[] first, int[] second) {
    Set<Integer> set = Arrays.stream(second).boxed().collect(Collectors.toSet());
    return Arrays.stream(first)
            .filter(e -> !set.contains(e))
            .toArray();
}

public static int[] distinctValuesOfArray(int[] first, int[] second) {
    return IntStream.concat(IntStream.of(first), IntStream.of(second))
            .distinct()
            .toArray();
}

public static int[] everyNth(int[] elements, int nth) {
    return IntStream.range(0, elements.length)
            .filter(i -> i % nth == nth - 1)
            .map(i -> elements[i])
            .toArray();
}

public static int indexOf(int[] elements, int value) {
    return IntStream.range(0, elements.length)
            .filter(i -> elements[i] == value)
            .findFirst()
            .orElse(-1);
}

public static int lastIndexOf(int[] elements, int value) {
    return IntStream.iterate(elements.length - 1, i -> i - 1)
            .limit(elements.length)
            .filter(i -> elements[i] == value)
            .findFirst()
            .orElse(-1);
}

public static int[] filterNonUnique(int[] elements) {
    return Arrays.stream(elements)
            .filter(e -> indexOf(elements, e) == lastIndexOf(elements, e))
            .toArray();
}

public static int[] initializeArrayWithRange(int start, int end) {
    return IntStream.rangeClosed(start, end).toArray();
}

public static int[] initializeArrayWithValues(int n, int value) {
    return IntStream.generate(() -> value).limit(n).toArray();
}

public static int[] intersection(int[] first, int[] second) {
    Set<Integer> set = Arrays.stream(second).boxed().collect(Collectors.toSet());
    return Arrays.stream(first)
            .filter(set::contains)
            .toArray();
}

public static <T> T nthElement(T[] arr, int n) {
    if (n > 0) {
        return Arrays.copyOfRange(arr, n, arr.length)[0];
    }
    return Arrays.copyOfRange(arr, arr.length + n, arr.length)[0];
}

public static <T, R> Map<T, R> pick(Map<T, R> obj, T[] arr) {
    return Arrays.stream(arr)
            .filter(obj::containsKey)
            .collect(Collectors.toMap(k -> k, obj::get));
}

public static <T> T sample(T[] arr) {
    return arr[(int) Math.floor(Math.random() * arr.length)];
}

public static <T> T[] shuffle(T[] input) {
    T[] arr = Arrays.copyOf(input, input.length);
    int length = arr.length;
    int m = length;
    while (m > 0) {
        int i = (int) Math.floor(Math.random() * m--);
        T tmp = arr[i];
        arr[i] = arr[m];
        arr[m] = tmp;
    }
    return arr;
}

public static <T> T[] sampleSize(T[] input, int n) {
    T[] arr = shuffle(input);
    return Arrays.copyOfRange(arr, 0, n > arr.length ? arr.length : n);
}

public static <T> T[] similarity(T[] first, T[] second) {
    return Arrays.stream(first)
            .filter(a -> Arrays.stream(second).anyMatch(b -> Objects.equals(a, b)))
            .toArray(i -> (T[]) Arrays.copyOf(new Object[0], i, first.getClass()));
}

public static <T> T[] symmetricDifference(T[] first, T[] second) {
    Set<T> sA = new HashSet<>(Arrays.asList(first));
    Set<T> sB = new HashSet<>(Arrays.asList(second));

    return Stream.concat(
            Arrays.stream(first).filter(a -> !sB.contains(a)),
            Arrays.stream(second).filter(b -> !sA.contains(b))
    ).toArray(i -> (T[]) Arrays.copyOf(new Object[0], i, first.getClass()));
}

public static <T> T[] union(T[] first, T[] second) {
    Set<T> set = new HashSet<>(Arrays.asList(first));
    set.addAll(Arrays.asList(second));
    return set.toArray((T[]) Arrays.copyOf(new Object[0], 0, first.getClass()));
}

public static <T> T[] without(T[] arr, T... elements) {
    List<T> excludeElements = Arrays.asList(elements);
    return Arrays.stream(arr)
            .filter(el -> !excludeElements.contains(el))
            .toArray(i -> (T[]) Arrays.copyOf(new Object[0], i, arr.getClass()));
}

public static double average(int[] arr) {
    return IntStream.of(arr)
            .average()
            .orElseThrow(() -> new IllegalArgumentException("Array is empty"));
}

public static boolean isEven(final int value) {
    return (value & 0b1) == 0;
}

public static int generateRandomInt() {
    return ThreadLocalRandom.current().nextInt();
}

public static List<String> anagrams(String input) {
    if (input.length() <= 2) {
        return input.length() == 2
                ? Arrays.asList(input, input.substring(1) + input.substring(0, 1))
                : Collections.singletonList(input);
    }
    return IntStream.range(0, input.length())
            .mapToObj(i -> new AbstractMap.SimpleEntry<>(i, input.substring(i, i + 1)))
            .flatMap(entry ->
                    anagrams(input.substring(0, entry.getKey()) + input.substring(entry.getKey() + 1))
                            .stream()
                            .map(s -> entry.getValue() + s))
            .collect(Collectors.toList());
}

public static boolean isNumeric(final String input) {
    return IntStream.range(0, input.length())
            .allMatch(i -> Character.isDigit(input.charAt(i)));
}

public static String reverseString(String input) {
    return new StringBuilder(input).reverse().toString();
}

public static String[] splitLines(String input) {
    return input.split("\\r?\\n");
}

public static int[] stringToIntegers(String numbers) {
    return Arrays.stream(numbers.split(" ")).mapToInt(Integer::parseInt).toArray();
}

public static <E extends Enum<E>> Map<String, E> getEnumMap(final Class<E> enumClass) {
    return Arrays.stream(enumClass.getEnumConstants())
            .collect(Collectors.toMap(Enum::name, Function.identity()));
}

public String readFileAsString(Path path) throws IOException {
    return new String(Files.readAllBytes(path));
}

public static String getCurrentWorkingDirectoryPath() {
    return FileSystems.getDefault().getPath("").toAbsolutePath().toString();
}

public static String stackTraceAsString(final Throwable throwable) {
    final StringWriter sw = new StringWriter();
    throwable.printStackTrace(new PrintWriter(sw));
    return sw.toString();
}