it.unimi.dsi.fastutil.ints.IntArraySet Maven / Gradle / Ivy
/*
* 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.ints;
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 IntArraySet extends AbstractIntSet implements java.io.Serializable, Cloneable {
private static final long serialVersionUID = 1L;
/** The backing array (valid up to {@link #size}, excluded). */
private transient int[] 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 a are distinct.
*
* @param a the backing array.
*/
public IntArraySet(final int[] a) {
this.a = a;
size = a.length;
}
/** Creates a new empty array set.
*/
public IntArraySet() {
this.a = IntArrays.EMPTY_ARRAY;
}
/** Creates a new empty array set of given initial capacity.
*
* @param capacity the initial capacity.
*/
public IntArraySet(final int capacity) {
this.a = new int[capacity];
}
/** Creates a new array set copying the contents of a given collection.
* @param c a collection.
*/
public IntArraySet(IntCollection c) {
this(c.size ());
addAll(c);
}
/** Creates a new array set copying the contents of a given set.
* @param c a collection.
*/
public IntArraySet(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 size elements of a are distinct.
*
* @param a the backing array.
* @param size the number of valid elements in a.
*/
public IntArraySet(final int[] 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 int o) {
for(int i = size; i-- != 0;) if (( (a[i]) == (o) )) return i;
return -1;
}
@Override
public IntIterator iterator() {
return new AbstractIntIterator () {
int next = 0;
@Override
public boolean hasNext() {
return next < size;
}
@Override
public int nextInt() {
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 int k) {
return findKey(k) != -1;
}
@Override
public int size() {
return size;
}
@Override
public boolean remove(final int 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 int k) {
final int pos = findKey(k);
if (pos != -1) return false;
if (size == a.length) {
final int[] b = new int[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 IntArraySet clone() {
IntArraySet c;
try {
c = (IntArraySet )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.writeInt(a[i]);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
a = new int[size];
for(int i = 0; i < size; i++) a[i] = s.readInt();
}
}