it.unimi.dsi.fastutil.ints.IntOpenHashSet Maven / Gradle / Ivy
Show all versions of fastutil Show documentation
/*
* Copyright (C) 2002-2017 Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package it.unimi.dsi.fastutil.ints;
import it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
/** A type-specific hash set with with a fast, small-footprint implementation.
*
* Instances of this class use a hash table to represent a set. The table is
* enlarged as needed by doubling its size when new entries are created, but it is never made
* smaller (even on a {@link #clear()}). A family of {@linkplain #trim() trimming
* methods} lets you control the size of the table; this is particularly useful
* if you reuse instances of this class.
*
* @see Hash
* @see HashCommon
*/
public class IntOpenHashSet extends AbstractIntSet implements java.io.Serializable, Cloneable, Hash {
private static final long serialVersionUID = 0L;
private static final boolean ASSERTS = false;
/** The array of keys. */
protected transient int[] key;
/** The mask for wrapping a position counter. */
protected transient int mask;
/** Whether this set contains the null key. */
protected transient boolean containsNull;
/** The current table size. Note that an additional element is allocated for storing the null key. */
protected transient int n;
/** Threshold after which we rehash. It must be the table size times {@link #f}. */
protected transient int maxFill;
/** Number of entries in the set (including the null key, if present). */
protected int size;
/** The acceptable load factor. */
protected final float f;
/** Creates a new hash set.
*
*
The actual table size will be the least power of two greater than expected/f.
*
* @param expected the expected number of elements in the hash set.
* @param f the load factor.
*/
public IntOpenHashSet(final int expected, final float f) {
if (f <= 0 || f > 1) throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than or equal to 1");
if (expected < 0) throw new IllegalArgumentException("The expected number of elements must be nonnegative");
this.f = f;
n = arraySize(expected, f);
mask = n - 1;
maxFill = maxFill(n, f);
key = new int[n + 1];
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*
* @param expected the expected number of elements in the hash set.
*/
public IntOpenHashSet(final int expected) {
this(expected, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set with initial expected {@link Hash#DEFAULT_INITIAL_SIZE} elements
* and {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*/
public IntOpenHashSet() {
this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying a given collection.
*
* @param c a {@link Collection} to be copied into the new hash set.
* @param f the load factor.
*/
public IntOpenHashSet(final Collection c, final float f) {
this(c.size(), f);
addAll(c);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given collection.
*
* @param c a {@link Collection} to be copied into the new hash set.
*/
public IntOpenHashSet(final Collection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying a given type-specific collection.
*
* @param c a type-specific collection to be copied into the new hash set.
* @param f the load factor.
*/
public IntOpenHashSet(final IntCollection c, final float f) {
this(c.size(), f);
addAll(c);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given type-specific collection.
*
* @param c a type-specific collection to be copied into the new hash set.
*/
public IntOpenHashSet(final IntCollection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set using elements provided by a type-specific iterator.
*
* @param i a type-specific iterator whose elements will fill the set.
* @param f the load factor.
*/
public IntOpenHashSet(final IntIterator i, final float f) {
this(DEFAULT_INITIAL_SIZE, f);
while(i.hasNext()) add(i.nextInt());
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor using elements provided by a type-specific iterator.
*
* @param i a type-specific iterator whose elements will fill the set.
*/
public IntOpenHashSet(final IntIterator i) {
this(i, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set using elements provided by an iterator.
*
* @param i an iterator whose elements will fill the set.
* @param f the load factor.
*/
public IntOpenHashSet(final Iterator i, final float f) {
this(IntIterators.asIntIterator(i), f);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor using elements provided by an iterator.
*
* @param i an iterator whose elements will fill the set.
*/
public IntOpenHashSet(final Iterator i) {
this(IntIterators.asIntIterator(i));
}
/** Creates a new hash set and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the set.
* @param offset the first element to use.
* @param length the number of elements to use.
* @param f the load factor.
*/
public IntOpenHashSet(final int[] a, final int offset, final int length, final float f) {
this(length < 0 ? 0 : length, f);
IntArrays.ensureOffsetLength(a, offset, length);
for(int i = 0; i < length; i++) add(a[offset + i]);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor and fills it with the elements of a given array.
*
* @param a an array whose elements will be used to fill the set.
* @param offset the first element to use.
* @param length the number of elements to use.
*/
public IntOpenHashSet(final int[] a, final int offset, final int length) {
this(a, offset, length, DEFAULT_LOAD_FACTOR);
}
/** Creates a new hash set copying the elements of an array.
*
* @param a an array to be copied into the new hash set.
* @param f the load factor.
*/
public IntOpenHashSet(final int[] a, final float f) {
this(a, 0, a.length, f);
}
/** Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying the elements of an array.
*
* @param a an array to be copied into the new hash set.
*/
public IntOpenHashSet(final int[] a) {
this(a, DEFAULT_LOAD_FACTOR);
}
private int realSize() {
return containsNull ? size - 1 : size;
}
private void ensureCapacity(final int capacity) {
final int needed = arraySize(capacity, f);
if (needed > n) rehash(needed);
}
private void tryCapacity(final long capacity) {
final int needed = (int)Math.min(1 << 30, Math.max(2, HashCommon.nextPowerOfTwo((long)Math.ceil(capacity / f))));
if (needed > n) rehash(needed);
}
@Override
public boolean addAll(IntCollection c) {
if (f <= .5) ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
else tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size() elements
return super.addAll(c);
}
@Override
public boolean addAll(Collection c) {
// The resulting collection will be at least c.size() big
if (f <= .5) ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
else tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size() elements
return super.addAll(c);
}
@Override
public boolean add(final int k) {
int pos;
if (( (k) == (0) )) {
if (containsNull) return false;
containsNull = true;
}
else {
int curr;
final int[] key = this.key;
// The starting point.
if (! ( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k) ) ) & mask]) == (0) )) {
if (( (curr) == (k) )) return false;
while(! ( (curr = key[pos = (pos + 1) & mask]) == (0) ))
if (( (curr) == (k) )) return false;
}
key[pos] = k;
}
if (size++ >= maxFill) rehash(arraySize(size + 1, f));
if (ASSERTS) checkTable();
return true;
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry.
*
* @param pos a starting position.
*/
protected final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
int curr;
final int[] key = this.key;
for(;;) {
pos = ((last = pos) + 1) & mask;
for(;;) {
if (( (curr = key[pos]) == (0) )) {
key[last] = (0);
return;
}
slot = ( it.unimi.dsi.fastutil.HashCommon.mix( (curr) ) ) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break;
pos = (pos + 1) & mask;
}
key[last] = curr;
}
}
private boolean removeEntry(final int pos) {
size--;
shiftKeys(pos);
if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2);
return true;
}
private boolean removeNullEntry() {
containsNull = false;
key[n] = (0);
size--;
if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2);
return true;
}
@Override
public boolean remove(final int k) {
if (( (k) == (0) )) {
if (containsNull) return removeNullEntry();
return false;
}
int curr;
final int[] key = this.key;
int pos;
// The starting point.
if (( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k) ) ) & mask]) == (0) )) return false;
if (( (k) == (curr) )) return removeEntry(pos);
while(true) {
if (( (curr = key[pos = (pos + 1) & mask]) == (0) )) return false;
if (( (k) == (curr) )) return removeEntry(pos);
}
}
@Override
public boolean contains(final int k) {
if (( (k) == (0) )) return containsNull;
int curr;
final int[] key = this.key;
int pos;
// The starting point.
if (( (curr = key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k) ) ) & mask]) == (0) )) return false;
if (( (k) == (curr) )) return true;
while(true) {
if (( (curr = key[pos = (pos + 1) & mask]) == (0) )) return false;
if (( (k) == (curr) )) return true;
}
}
/* Removes all elements from this set.
*
*
To increase object reuse, this method does not change the table size.
* If you want to reduce the table size, you must use {@link #trim()}.
*
*/
@Override
public void clear() {
if (size == 0) return;
size = 0;
containsNull = false;
Arrays.fill(key, (0));
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/** A no-op for backward compatibility.
*
* @param growthFactor unused.
* @deprecated Since fastutil 6.1.0, hash tables are doubled when they are too full.
*/
@Deprecated
public void growthFactor(int growthFactor) {}
/** Gets the growth factor (2).
*
* @return the growth factor of this set, which is fixed (2).
* @see #growthFactor(int)
* @deprecated Since fastutil 6.1.0, hash tables are doubled when they are too full.
*/
@Deprecated
public int growthFactor() {
return 16;
}
/** An iterator over a hash set. */
private class SetIterator extends AbstractIntIterator {
/** The index of the last entry returned, if positive or zero; initially, {@link #n}. If negative, the last
element returned was that of index {@code - pos - 1} from the {@link #wrapped} list. */
int pos = n;
/** The index of the last entry that has been returned (more precisely, the value of {@link #pos} if {@link #pos} is positive,
or {@link Integer#MIN_VALUE} if {@link #pos} is negative). It is -1 if either
we did not return an entry yet, or the last returned entry has been removed. */
int last = -1;
/** A downward counter measuring how many entries must still be returned. */
int c = size;
/** A boolean telling us whether we should return the null key. */
boolean mustReturnNull = IntOpenHashSet.this.containsNull;
/** A lazily allocated list containing elements that have wrapped around the table because of removals. */
IntArrayList wrapped;
public boolean hasNext() {
return c != 0;
}
public int nextInt() {
if (! hasNext()) throw new NoSuchElementException();
c--;
if (mustReturnNull) {
mustReturnNull = false;
last = n;
return key[n];
}
final int key[] = IntOpenHashSet.this.key;
for(;;) {
if (--pos < 0) {
// We are just enumerating elements from the wrapped list.
last = Integer.MIN_VALUE;
return wrapped.getInt(- pos - 1);
}
if (! ( (key[pos]) == (0) )) return key[last = pos];
}
}
/** Shifts left entries with the specified hash code, starting at the specified position,
* and empties the resulting free entry.
*
* @param pos a starting position.
*/
private final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
int curr;
final int[] key = IntOpenHashSet.this.key;
for(;;) {
pos = ((last = pos) + 1) & mask;
for(;;) {
if (( (curr = key[pos]) == (0) )) {
key[last] = (0);
return;
}
slot = ( it.unimi.dsi.fastutil.HashCommon.mix( (curr) ) ) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break;
pos = (pos + 1) & mask;
}
if (pos < last) { // Wrapped entry.
if (wrapped == null) wrapped = new IntArrayList (2);
wrapped.add(key[pos]);
}
key[last] = curr;
}
}
public void remove() {
if (last == -1) throw new IllegalStateException();
if (last == n) {
IntOpenHashSet.this.containsNull = false;
IntOpenHashSet.this.key[n] = (0);
}
else if (pos >= 0) shiftKeys(last);
else {
// We're removing wrapped entries.
IntOpenHashSet.this.remove(wrapped.getInt(- pos - 1));
last = -1; // Note that we must not decrement size
return;
}
size--;
last = -1; // You can no longer remove this entry.
if (ASSERTS) checkTable();
}
}
@Override
public IntIterator iterator() {
return new SetIterator();
}
/** A no-op for backward compatibility. The kind of tables implemented by
* this class never need rehashing.
*
*
If you need to reduce the table size to fit exactly
* this set, use {@link #trim()}.
*
* @return true.
* @see #trim()
* @deprecated A no-op.
*/
@Deprecated
public boolean rehash() {
return true;
}
/** Rehashes this set, making the table as small as possible.
*
*
This method rehashes the table to the smallest size satisfying the
* load factor. It can be used when the set will not be changed anymore, so
* to optimize access speed and size.
*
*
If the table size is already the minimum possible, this method
* does nothing.
*
* @return true if there was enough memory to trim the set.
* @see #trim(int)
*/
public boolean trim() {
final int l = arraySize(size, f);
if (l >= n || size > maxFill(l, f)) return true;
try {
rehash(l);
}
catch(OutOfMemoryError cantDoIt) { return false; }
return true;
}
/** Rehashes this set if the table is too large.
*
*
Let N be the smallest table size that can hold
* max(n,{@link #size()}) entries, still satisfying the load factor. If the current
* table size is smaller than or equal to N, this method does
* nothing. Otherwise, it rehashes this set in a table of size
* N.
*
*
This method is useful when reusing sets. {@linkplain #clear() Clearing a
* set} leaves the table size untouched. If you are reusing a set
* many times, you can call this method with a typical
* size to avoid keeping around a very large table just
* because of a few large transient sets.
*
* @param n the threshold for the trimming.
* @return true if there was enough memory to trim the set.
* @see #trim()
*/
public boolean trim(final int n) {
final int l = HashCommon.nextPowerOfTwo((int)Math.ceil(n / f));
if (l >= n || size > maxFill(l, f)) return true;
try {
rehash(l);
}
catch(OutOfMemoryError cantDoIt) { return false; }
return true;
}
/** Rehashes the set.
*
*
This method implements the basic rehashing strategy, and may be
* overriden by subclasses implementing different rehashing strategies (e.g.,
* disk-based rehashing). However, you should not override this method
* unless you understand the internal workings of this class.
*
* @param newN the new size
*/
protected void rehash(final int newN) {
final int key[] = this.key;
final int mask = newN - 1; // Note that this is used by the hashing macro
final int newKey[] = new int[newN + 1];
int i = n, pos;
for(int j = realSize(); j-- != 0;) {
while(( (key[--i]) == (0) ));
if (! ( (newKey[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (key[i]) ) ) & mask]) == (0) ))
while (! ( (newKey[pos = (pos + 1) & mask]) == (0) ));
newKey[pos] = key[i];
}
n = newN;
this.mask = mask;
maxFill = maxFill(n, f);
this.key = newKey;
}
/** Returns a deep copy of this set.
*
*
This method performs a deep copy of this hash set; the data stored in the
* set, however, is not cloned. Note that this makes a difference only for object keys.
*
* @return a deep copy of this set.
*/
@Override
public IntOpenHashSet clone() {
IntOpenHashSet c;
try {
c = (IntOpenHashSet )super.clone();
}
catch(CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.key = key.clone();
c.containsNull = containsNull;
return c;
}
/** Returns a hash code for this set.
*
* This method overrides the generic method provided by the superclass.
* Since equals() is not overriden, it is important
* that the value returned by this method is the same value as
* the one returned by the overriden method.
*
* @return a hash code for this set.
*/
@Override
public int hashCode() {
int h = 0;
for(int j = realSize(), i = 0; j-- != 0;) {
while(( (key[i]) == (0) )) i++;
h += (key[i]);
i++;
}
// Zero / null have hash zero.
return h;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
final IntIterator i = iterator();
s.defaultWriteObject();
for(int j = size; j-- != 0;) s.writeInt(i.nextInt());
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
n = arraySize(size, f);
maxFill = maxFill(n, f);
mask = n - 1;
final int key[] = this.key = new int[n + 1];
int k;
for(int i = size, pos; i-- != 0;) {
k = s.readInt();
if (( (k) == (0) )) {
pos = n;
containsNull = true;
}
else {
if (! ( (key[pos = ( it.unimi.dsi.fastutil.HashCommon.mix( (k) ) ) & mask]) == (0) ))
while (! ( (key[pos = (pos + 1) & mask]) == (0) ));
}
key[pos] = k;
}
if (ASSERTS) checkTable();
}
private void checkTable() {}
}