implements java.io.Serializable {

@java.io.Serial

private static final long serialVersionUID = -7720805057305804111L;

private static final int DEFAULT_INITIAL_CAPACITY = 11;

/**

transient Object[] queue; // non-private to simplify nested class access

/**

int size;

/**

@SuppressWarnings("serial") // Conditionally serializable

private final Comparator<? super E> comparator;

/**

transient int modCount; // non-private to simplify nested class access

/**

public PriorityQueue() {

this(DEFAULT_INITIAL_CAPACITY, null);

}

/**

public PriorityQueue(int initialCapacity) {

this(initialCapacity, null);

}

/**

public PriorityQueue(Comparator<? super E> comparator) {

this(DEFAULT_INITIAL_CAPACITY, comparator);

}

/**

public PriorityQueue(int initialCapacity,

Comparator<? super E> comparator) {

// Note: This restriction of at least one is not actually needed,

// but continues for 1.5 compatibility

if (initialCapacity < 1)

throw new IllegalArgumentException();

this.queue = new Object[initialCapacity];

this.comparator = comparator;

}

/**

public PriorityQueue(Collection<? extends E> c) {

if (c instanceof SortedSet<?>) {

SortedSet<? extends E> ss = (SortedSet<? extends E>) c;

this.comparator = (Comparator<? super E>) ss.comparator();

initElementsFromCollection(ss);

}

else if (c instanceof PriorityQueue<?>) {

PriorityQueue<? extends E> pq = (PriorityQueue<? extends E>) c;

this.comparator = (Comparator<? super E>) pq.comparator();

initFromPriorityQueue(pq);

}

else {

this.comparator = null;

initFromCollection(c);

}

}

/**

public PriorityQueue(Collection<? extends E> c,

Comparator<? super E> comparator) {

this.comparator = comparator;

if (c instanceof SortedSet<? extends E> ss && comparator == ss.comparator()) {

initElementsFromCollection(ss);

} else if (c instanceof PriorityQueue<? extends E> pq && comparator == pq.comparator()) {

initFromPriorityQueue(pq);

} else {

initFromCollection(c);

}

}

/**

public PriorityQueue(PriorityQueue<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initFromPriorityQueue(c);

}

/**

public PriorityQueue(SortedSet<? extends E> c) {

this.comparator = (Comparator<? super E>) c.comparator();

initElementsFromCollection(c);

}

/** Ensures that queue[0] exists, helping peek() and poll(). */

private static Object[] ensureNonEmpty(Object[] es) {

return (es.length > 0) ? es : new Object[1];

}

private void initFromPriorityQueue(PriorityQueue<? extends E> c) {

if (c.getClass() == PriorityQueue.class) {

this.queue = ensureNonEmpty(c.toArray());

this.size = c.size();

} else {

initFromCollection(c);

}

}

private void initElementsFromCollection(Collection<? extends E> c) {

Object[] es = c.toArray();

int len = es.length;

if (c.getClass() != ArrayList.class)

es = Arrays.copyOf(es, len, Object[].class);

if (len == 1 || this.comparator != null)

for (Object e : es)

if (e == null)

throw new NullPointerException();

this.queue = ensureNonEmpty(es);

this.size = len;

}

/**

private void initFromCollection(Collection<? extends E> c) {

initElementsFromCollection(c);

heapify();

}

/**

private void grow(int minCapacity) {

int oldCapacity = queue.length;

// Double size if small; else grow by 50%

int newCapacity = ArraysSupport.newLength(oldCapacity,

minCapacity - oldCapacity, /* minimum growth */

oldCapacity < 64 ? oldCapacity + 2 : oldCapacity >> 1

/* preferred growth */);

queue = Arrays.copyOf(queue, newCapacity);

}

/**

public boolean add(E e) {

return offer(e);

}

/**

public boolean offer(E e) {

if (e == null)

throw new NullPointerException();

modCount++;

int i = size;

if (i >= queue.length)

grow(i + 1);

siftUp(i, e);

size = i + 1;

return true;

}

public E peek() {

return (E) queue[0];

}

private int indexOf(Object o) {

if (o != null) {

final Object[] es = queue;

for (int i = 0, n = size; i < n; i++)

if (o.equals(es[i]))

return i;

}

return -1;

}

/**

public boolean remove(Object o) {

int i = indexOf(o);

if (i == -1)

return false;

else {

removeAt(i);

return true;

}

}

/**

void removeEq(Object o) {

final Object[] es = queue;

for (int i = 0, n = size; i < n; i++) {

if (o == es[i]) {

removeAt(i);

break;

}

}

}

/**

public boolean contains(Object o) {

return indexOf(o) >= 0;

}

/**

public Object[] toArray() {

return Arrays.copyOf(queue, size);

}

/**

public <T> T[] toArray(T[] a) {

final int size = this.size;

if (a.length < size)

// Make a new array of a's runtime type, but my contents:

return (T[]) Arrays.copyOf(queue, size, a.getClass());

System.arraycopy(queue, 0, a, 0, size);

if (a.length > size)

a[size] = null;

return a;

}

/**

public Iterator<E> iterator() {

return new Itr();

}

private final class Itr implements Iterator<E> {

/**

private int cursor;

/**

private int lastRet = -1;

/**

private ArrayDeque<E> forgetMeNot;

/**

private E lastRetElt;

/**

private int expectedModCount = modCount;

Itr() {} // prevent access constructor creation

public boolean hasNext() {

return cursor < size ||

(forgetMeNot != null && !forgetMeNot.isEmpty());

}

public E next() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (cursor < size)

return (E) queue[lastRet = cursor++];

if (forgetMeNot != null) {

lastRet = -1;

lastRetElt = forgetMeNot.poll();

if (lastRetElt != null)

return lastRetElt;

}

throw new NoSuchElementException();

}

public void remove() {

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

if (lastRet != -1) {

E moved = PriorityQueue.this.removeAt(lastRet);

lastRet = -1;

if (moved == null)

cursor--;

else {

if (forgetMeNot == null)

forgetMeNot = new ArrayDeque<>();

forgetMeNot.add(moved);

}

} else if (lastRetElt != null) {

PriorityQueue.this.removeEq(lastRetElt);

lastRetElt = null;

} else {

throw new IllegalStateException();

}

expectedModCount = modCount;

}

}

public int size() {

return size;

}

/**

public void clear() {

modCount++;

final Object[] es = queue;

for (int i = 0, n = size; i < n; i++)

es[i] = null;

size = 0;

}

public E poll() {

final Object[] es;

final E result;

if ((result = (E) ((es = queue)[0])) != null) {

modCount++;

final int n;

final E x = (E) es[(n = --size)];

es[n] = null;

if (n > 0) {

final Comparator<? super E> cmp;

if ((cmp = comparator) == null)

siftDownComparable(0, x, es, n);

else

siftDownUsingComparator(0, x, es, n, cmp);

}

}

return result;

}

/**

E removeAt(int i) {

// assert i >= 0 && i < size;

final Object[] es = queue;

modCount++;

int s = --size;

if (s == i) // removed last element

es[i] = null;

else {

E moved = (E) es[s];

es[s] = null;

siftDown(i, moved);

if (es[i] == moved) {

siftUp(i, moved);

if (es[i] != moved)

return moved;

}

}

return null;

}

/**

private void siftUp(int k, E x) {

if (comparator != null)

siftUpUsingComparator(k, x, queue, comparator);

else

siftUpComparable(k, x, queue);

}

private static <T> void siftUpComparable(int k, T x, Object[] es) {

Comparable<? super T> key = (Comparable<? super T>) x;

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = es[parent];

if (key.compareTo((T) e) >= 0)

break;

es[k] = e;

k = parent;

}

es[k] = key;

}

private static <T> void siftUpUsingComparator(

int k, T x, Object[] es, Comparator<? super T> cmp) {

while (k > 0) {

int parent = (k - 1) >>> 1;

Object e = es[parent];

if (cmp.compare(x, (T) e) >= 0)

break;

es[k] = e;

k = parent;

}

es[k] = x;

}

/**

private void siftDown(int k, E x) {

if (comparator != null)

siftDownUsingComparator(k, x, queue, size, comparator);

else

siftDownComparable(k, x, queue, size);

}

private static <T> void siftDownComparable(int k, T x, Object[] es, int n) {

// assert n > 0;

Comparable<? super T> key = (Comparable<? super T>)x;

int half = n >>> 1; // loop while a non-leaf

while (k < half) {

int child = (k << 1) + 1; // assume left child is least

Object c = es[child];

int right = child + 1;

if (right < n &&

((Comparable<? super T>) c).compareTo((T) es[right]) > 0)

c = es[child = right];

if (key.compareTo((T) c) <= 0)

break;

es[k] = c;

k = child;

}

es[k] = key;

}

private static <T> void siftDownUsingComparator(

int k, T x, Object[] es, int n, Comparator<? super T> cmp) {

// assert n > 0;

int half = n >>> 1;

while (k < half) {

int child = (k << 1) + 1;

Object c = es[child];

int right = child + 1;

if (right < n && cmp.compare((T) c, (T) es[right]) > 0)

c = es[child = right];

if (cmp.compare(x, (T) c) <= 0)

break;

es[k] = c;

k = child;

}

es[k] = x;

}

/**

private void heapify() {

final Object[] es = queue;

int n = size, i = (n >>> 1) - 1;

final Comparator<? super E> cmp;

if ((cmp = comparator) == null)

for (; i >= 0; i--)

siftDownComparable(i, (E) es[i], es, n);

else

for (; i >= 0; i--)

siftDownUsingComparator(i, (E) es[i], es, n, cmp);

}

/**

public Comparator<? super E> comparator() {

return comparator;

}

/**

@java.io.Serial

private void writeObject(java.io.ObjectOutputStream s)

throws java.io.IOException {

// Write out element count, and any hidden stuff

s.defaultWriteObject();

// Write out array length, for compatibility with 1.5 version

s.writeInt(Math.max(2, size + 1));

// Write out all elements in the "proper order".

final Object[] es = queue;

for (int i = 0, n = size; i < n; i++)

s.writeObject(es[i]);

}

/**

@java.io.Serial

private void readObject(java.io.ObjectInputStream s)

throws java.io.IOException, ClassNotFoundException {

// Read in size, and any hidden stuff

s.defaultReadObject();

// Read in (and discard) array length

s.readInt();

SharedSecrets.getJavaObjectInputStreamAccess().checkArray(s, Object[].class, size);

final Object[] es = queue = new Object[Math.max(size, 1)];

// Read in all elements.

for (int i = 0, n = size; i < n; i++)

es[i] = s.readObject();

// Elements are guaranteed to be in "proper order", but the

// spec has never explained what that might be.

heapify();

}

/**

public final Spliterator<E> spliterator() {

return new PriorityQueueSpliterator(0, -1, 0);

}

final class PriorityQueueSpliterator implements Spliterator<E> {

private int index; // current index, modified on advance/split

private int fence; // -1 until first use

private int expectedModCount; // initialized when fence set

/** Creates new spliterator covering the given range. */

PriorityQueueSpliterator(int origin, int fence, int expectedModCount) {

this.index = origin;

this.fence = fence;

this.expectedModCount = expectedModCount;

}

private int getFence() { // initialize fence to size on first use

int hi;

if ((hi = fence) < 0) {

expectedModCount = modCount;

hi = fence = size;

}

return hi;

}

public PriorityQueueSpliterator trySplit() {

int hi = getFence(), lo = index, mid = (lo + hi) >>> 1;

return (lo >= mid) ? null :

new PriorityQueueSpliterator(lo, index = mid, expectedModCount);

}

public void forEachRemaining(Consumer<? super E> action) {

if (action == null)

throw new NullPointerException();

if (fence < 0) { fence = size; expectedModCount = modCount; }

final Object[] es = queue;

int i, hi; E e;

for (i = index, index = hi = fence; i < hi; i++) {

if ((e = (E) es[i]) == null)

break; // must be CME

action.accept(e);

}

if (modCount != expectedModCount)

throw new ConcurrentModificationException();

}

public boolean tryAdvance(Consumer<? super E> action) {

if (action == null)

throw new NullPointerException();

if (fence < 0) { fence = size; expectedModCount = modCount; }

int i;

if ((i = index) < fence) {

index = i + 1;

E e;

if ((e = (E) queue[i]) == null

|| modCount != expectedModCount)

throw new ConcurrentModificationException();

action.accept(e);

return true;

}

return false;

}

public long estimateSize() {

return getFence() - index;

}

public int characteristics() {

return Spliterator.SIZED | Spliterator.SUBSIZED | Spliterator.NONNULL;

}

}

/**

public boolean removeIf(Predicate<? super E> filter) {

Objects.requireNonNull(filter);

return bulkRemove(filter);

}

/**

public boolean removeAll(Collection<?> c) {

Objects.requireNonNull(c);

return bulkRemove(e -> c.contains(e));

}

/**

public boolean retainAll(Collection<?> c) {

Objects.requireNonNull(c);

return bulkRemove(e -> !c.contains(e));

}

// A tiny bit set implementation

private static long[] nBits(int n) {

return new long[((n - 1) >> 6) + 1];

}

private static void setBit(long[] bits, int i) {

bits[i >> 6] |= 1L << i;

}

private static boolean isClear(long[] bits, int i) {

return (bits[i >> 6] & (1L << i)) == 0;

}

/** Implementation of bulk remove methods. */

private boolean bulkRemove(Predicate<? super E> filter) {

final int expectedModCount = ++modCount;

final Object[] es = queue;

final int end = size;

int i;

// Optimize for initial run of survivors

for (i = 0; i < end && !filter.test((E) es[i]); i++)

;

if (i >= end) {

if (modCount != expectedModCount)

throw new ConcurrentModificationException();

return false;

}

// Tolerate predicates that reentrantly access the collection for

// read (but writers still get CME), so traverse once to find

// elements to delete, a second pass to physically expunge.

final int beg = i;

final long[] deathRow = nBits(end - beg);

deathRow[0] = 1L; // set bit 0

for (i = beg + 1; i < end; i++)

if (filter.test((E) es[i]))

setBit(deathRow, i - beg);

if (modCount != expectedModCount)

throw new ConcurrentModificationException();

int w = beg;

for (i = beg; i < end; i++)

if (isClear(deathRow, i - beg))

es[w++] = es[i];

for (i = size = w; i < end; i++)

es[i] = null;

heapify();

return true;

}

/**

public void forEach(Consumer<? super E> action) {

Objects.requireNonNull(action);

final int expectedModCount = modCount;

final Object[] es = queue;

for (int i = 0, n = size; i < n; i++)

action.accept((E) es[i]);

if (expectedModCount != modCount)

throw new ConcurrentModificationException();

}