it.unimi.dsi.fastutil.longs.LongArraySet Maven / Gradle / Ivy
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/*
* Copyright (C) 2007-2017 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.longs;
import java.util.Collection;
import java.util.NoSuchElementException;
/**
* A simple, brute-force implementation of a set based on a backing array.
*
*
* The main purpose of this implementation is that of wrapping cleanly the
* brute-force approach to the storage of a very small number of items: just put
* them into an array and scan linearly to find an item.
*/
public class LongArraySet extends AbstractLongSet implements java.io.Serializable, Cloneable {
private static final long serialVersionUID = 1L;
/** The backing array (valid up to {@link #size}, excluded). */
private transient long[] a;
/** The number of valid entries in {@link #a}. */
private int size;
/**
* Creates a new array set using the given backing array. The resulting set will
* have as many elements as the array.
*
*
* It is responsibility of the caller that the elements of {@code a} are
* distinct.
*
* @param a
* the backing array.
*/
public LongArraySet(final long[] a) {
this.a = a;
size = a.length;
}
/**
* Creates a new empty array set.
*/
public LongArraySet() {
this.a = LongArrays.EMPTY_ARRAY;
}
/**
* Creates a new empty array set of given initial capacity.
*
* @param capacity
* the initial capacity.
*/
public LongArraySet(final int capacity) {
this.a = new long[capacity];
}
/**
* Creates a new array set copying the contents of a given collection.
*
* @param c
* a collection.
*/
public LongArraySet(LongCollection c) {
this(c.size());
addAll(c);
}
/**
* Creates a new array set copying the contents of a given set.
*
* @param c
* a collection.
*/
public LongArraySet(final Collection c) {
this(c.size());
addAll(c);
}
/**
* Creates a new array set using the given backing array and the given number of
* elements of the array.
*
*
* It is responsibility of the caller that the first {@code size} elements of
* {@code a} are distinct.
*
* @param a
* the backing array.
* @param size
* the number of valid elements in {@code a}.
*/
public LongArraySet(final long[] a, final int size) {
this.a = a;
this.size = size;
if (size > a.length)
throw new IllegalArgumentException(
"The provided size (" + size + ") is larger than or equal to the array size (" + a.length + ")");
}
private int findKey(final long o) {
for (int i = size; i-- != 0;)
if (((a[i]) == (o)))
return i;
return -1;
}
@Override
public LongIterator iterator() {
return new LongIterator() {
int next = 0;
@Override
public boolean hasNext() {
return next < size;
}
@Override
public long nextLong() {
if (!hasNext())
throw new NoSuchElementException();
return a[next++];
}
@Override
public void remove() {
final int tail = size-- - next--;
System.arraycopy(a, next + 1, a, next, tail);
}
};
}
@Override
public boolean contains(final long k) {
return findKey(k) != -1;
}
@Override
public int size() {
return size;
}
@Override
public boolean remove(final long k) {
final int pos = findKey(k);
if (pos == -1)
return false;
final int tail = size - pos - 1;
for (int i = 0; i < tail; i++)
a[pos + i] = a[pos + i + 1];
size--;
return true;
}
@Override
public boolean add(final long k) {
final int pos = findKey(k);
if (pos != -1)
return false;
if (size == a.length) {
final long[] b = new long[size == 0 ? 2 : size * 2];
for (int i = size; i-- != 0;)
b[i] = a[i];
a = b;
}
a[size++] = k;
return true;
}
@Override
public void clear() {
size = 0;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/**
* Returns a deep copy of this set.
*
*
* This method performs a deep copy of this array 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 LongArraySet clone() {
LongArraySet c;
try {
c = (LongArraySet) super.clone();
} catch (CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.a = a.clone();
return c;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject();
for (int i = 0; i < size; i++)
s.writeLong(a[i]);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
a = new long[size];
for (int i = 0; i < size; i++)
a[i] = s.readLong();
}
}