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* Copyright (C) 2003-2016 Paolo Boldi and Sebastiano Vigna
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package it.unimi.dsi.fastutil.longs;
import java.util.NoSuchElementException;
import it.unimi.dsi.fastutil.ints.IntArrays;
import it.unimi.dsi.fastutil.AbstractIndirectPriorityQueue;
/**
* A type-specific heap-based semi-indirect priority queue.
*
*
* Instances of this class use as reference list a reference array,
* which must be provided to each constructor. The priority queue is represented
* using a heap. The heap is enlarged as needed, but it is never shrunk. Use the
* {@link #trim()} method to reduce its size, if necessary.
*
*
* This implementation allows one to enqueue several time the same index, but
* you must be careful when calling {@link #changed()}.
*/
public class LongHeapSemiIndirectPriorityQueue extends AbstractIndirectPriorityQueue implements LongIndirectPriorityQueue {
/** The reference array. */
protected final long refArray[];
/** The semi-indirect heap. */
protected int heap[] = IntArrays.EMPTY_ARRAY;
/** The number of elements in this queue. */
protected int size;
/** The type-specific comparator used in this queue. */
protected LongComparator c;
/**
* Creates a new empty queue without elements with a given capacity and
* comparator.
*
* @param refArray
* the reference array.
* @param capacity
* the initial capacity of this queue.
* @param c
* the comparator used in this queue, or null for
* the natural order.
*/
public LongHeapSemiIndirectPriorityQueue(long[] refArray, int capacity, LongComparator c) {
if (capacity > 0) this.heap = new int[capacity];
this.refArray = refArray;
this.c = c;
}
/**
* Creates a new empty queue with given capacity and using the natural
* order.
*
* @param refArray
* the reference array.
* @param capacity
* the initial capacity of this queue.
*/
public LongHeapSemiIndirectPriorityQueue(long[] refArray, int capacity) {
this(refArray, capacity, null);
}
/**
* Creates a new empty queue with capacity equal to the length of the
* reference array and a given comparator.
*
* @param refArray
* the reference array.
* @param c
* the comparator used in this queue, or null for
* the natural order.
*/
public LongHeapSemiIndirectPriorityQueue(long[] refArray, LongComparator c) {
this(refArray, refArray.length, c);
}
/**
* Creates a new empty queue with capacity equal to the length of the
* reference array and using the natural order.
*
* @param refArray
* the reference array.
*/
public LongHeapSemiIndirectPriorityQueue(final long[] refArray) {
this(refArray, refArray.length, null);
}
/**
* Wraps a given array in a queue using a given comparator.
*
*
* The queue returned by this method will be backed by the given array. The
* first size element of the array will be rearranged so to
* form a heap (this is more efficient than enqueing the elements of
* a one by one).
*
* @param refArray
* the reference array.
* @param a
* an array of indices into refArray.
* @param size
* the number of elements to be included in the queue.
* @param c
* the comparator used in this queue, or null for
* the natural order.
*/
public LongHeapSemiIndirectPriorityQueue(final long[] refArray, final int[] a, int size, final LongComparator c) {
this(refArray, 0, c);
this.heap = a;
this.size = size;
LongSemiIndirectHeaps.makeHeap(refArray, a, size, c);
}
/**
* Wraps a given array in a queue using a given comparator.
*
*
* The queue returned by this method will be backed by the given array. The
* elements of the array will be rearranged so to form a heap (this is more
* efficient than enqueing the elements of a one by one).
*
* @param refArray
* the reference array.
* @param a
* an array of indices into refArray.
* @param c
* the comparator used in this queue, or null for
* the natural order.
*/
public LongHeapSemiIndirectPriorityQueue(final long[] refArray, final int[] a, final LongComparator c) {
this(refArray, a, a.length, c);
}
/**
* Wraps a given array in a queue using the natural order.
*
*
* The queue returned by this method will be backed by the given array. The
* first size element of the array will be rearranged so to
* form a heap (this is more efficient than enqueing the elements of
* a one by one).
*
* @param refArray
* the reference array.
* @param a
* an array of indices into refArray.
* @param size
* the number of elements to be included in the queue.
*/
public LongHeapSemiIndirectPriorityQueue(final long[] refArray, final int[] a, int size) {
this(refArray, a, size, null);
}
/**
* Wraps a given array in a queue using the natural order.
*
*
* The queue returned by this method will be backed by the given array. The
* elements of the array will be rearranged so to form a heap (this is more
* efficient than enqueing the elements of a one by one).
*
* @param refArray
* the reference array.
* @param a
* an array of indices into refArray.
*/
public LongHeapSemiIndirectPriorityQueue(final long[] refArray, final int[] a) {
this(refArray, a, a.length);
}
/**
* Ensures that the given index is a valid reference.
*
* @param index
* an index in the reference array.
* @throws IndexOutOfBoundsException
* if the given index is negative or larger than the reference
* array length.
*/
protected void ensureElement(final int index) {
if (index < 0) throw new IndexOutOfBoundsException("Index (" + index + ") is negative");
if (index >= refArray.length) throw new IndexOutOfBoundsException("Index (" + index + ") is larger than or equal to reference array size (" + refArray.length + ")");
}
public void enqueue(int x) {
ensureElement(x);
if (size == heap.length) heap = IntArrays.grow(heap, size + 1);
heap[size++] = x;
LongSemiIndirectHeaps.upHeap(refArray, heap, size, size - 1, c);
}
public int dequeue() {
if (size == 0) throw new NoSuchElementException();
final int result = heap[0];
heap[0] = heap[--size];
if (size != 0) LongSemiIndirectHeaps.downHeap(refArray, heap, size, 0, c);
return result;
}
public int first() {
if (size == 0) throw new NoSuchElementException();
return heap[0];
}
/**
* {@inheritDoc}
*
*
* The caller must guarantee that when this method is
* called the index of the first element appears just once in the queue.
* Failure to do so will bring the queue in an inconsistent state, and will
* cause unpredictable behaviour.
*/
public void changed() {
LongSemiIndirectHeaps.downHeap(refArray, heap, size, 0, c);
}
/**
* Rebuilds this heap in a bottom-up fashion.
*/
public void allChanged() {
LongSemiIndirectHeaps.makeHeap(refArray, heap, size, c);
}
public int size() {
return size;
}
public void clear() {
size = 0;
}
/**
* Trims the backing array so that it has exactly {@link #size()} elements.
*/
public void trim() {
heap = IntArrays.trim(heap, size);
}
public LongComparator comparator() {
return c;
}
public int front(final int[] a) {
return c == null ? LongSemiIndirectHeaps.front(refArray, heap, size, a) : LongSemiIndirectHeaps.front(refArray, heap, size, a, c);
}
public String toString() {
StringBuffer s = new StringBuffer();
s.append("[");
for (int i = 0; i < size; i++) {
if (i != 0) s.append(", ");
s.append(refArray[heap[i]]);
}
s.append("]");
return s.toString();
}
}