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LazyPriorityQueue.java
executable file
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LazyPriorityQueue.java
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/*
* Copyright 2020 Emory University
*
* 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 edu.emory.cs.queue;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/** @author Jinho D. Choi */
public class LazyPriorityQueue<T extends Comparable<T>> extends AbstractPriorityQueue<T> {
private final List<T> keys;
/** Initializes this as a maximum PQ. */
public LazyPriorityQueue() {
this(Comparator.naturalOrder());
}
/** @see AbstractPriorityQueue#AbstractPriorityQueue(Comparator). */
public LazyPriorityQueue(Comparator<T> priority) {
super(priority);
keys = new ArrayList<>();
}
@Override
public int size() {
return keys.size();
}
/**
* Appends a key to {@link #keys}.
* @param key the key to be added.
*/
@Override
public void add(T key) {
keys.add(key);
}
/**
* Finds the key with the highest/lowest priority, and removes it from {@link #keys}.
* @return the key with the highest/lowest priority if exists; otherwise, null.
*/
@Override
public T remove() {
if (isEmpty()) return null;
T max = Collections.max(keys, priority);
keys.remove(max);
return max;
}
}