src.it.unimi.dsi.fastutil.PriorityQueue Maven / Gradle / Ivy
package it.unimi.dsi.fastutil;
/*
* Copyright (C) 2003-2013 Paolo Boldi and 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.
*/
import java.util.Comparator;
import java.util.NoSuchElementException;
/** A priority queue.
*
* A priority queue provides a way to {@linkplain #enqueue(Object) enqueue}
* elements, and to {@linkplain #dequeue() dequeue} them in some specified
* order. Elements that are smaller in the specified order are
* dequeued first. It is also possible to get the {@linkplain #first() first
* element}, that is, the element that would be dequeued next.
*
*
Additionally, the queue may provide a method to peek at
* element that would be dequeued {@linkplain #last() last}.
*
*
The relative order of the elements enqueued should not change during
* queue operations. Nonetheless, some implementations may give the caller a
* way to notify the queue that the {@linkplain #changed() first element has
* changed its relative position in the order}.
*/
public interface PriorityQueue {
/** Enqueues a new element.
*
* @param x the element to enqueue..
*/
void enqueue( K x );
/** Dequeues the {@linkplain #first() first} element from the queue.
*
* @return the dequeued element.
* @throws NoSuchElementException if the queue is empty.
*/
K dequeue();
/** Checks whether the queue is empty.
*
* @return true if the queue is empty.
*/
boolean isEmpty();
/** Returns the number of elements in this queue.
*
* @return the number of elements in this queue.
*/
int size();
/** Removes all elements from this queue.
*/
void clear();
/** Returns the first element of the queue.
*
* @return the first element.
* @throws NoSuchElementException if the queue is empty.
*/
K first();
/** Returns the last element of the queue, that is, the element the would be dequeued last (optional operation).
*
* @return the last element.
* @throws NoSuchElementException if the queue is empty.
*/
K last();
/** Notifies the queue that the {@linkplain #first() first} element has changed (optional operation).
*/
void changed();
/** Returns the comparator associated with this queue, or null if it uses its elements' natural ordering.
*
* @return the comparator associated with this sorted set, or null if it uses its elements' natural ordering.
*/
Comparator comparator();
}