/
EagerPriorityQueue.java
executable file
·62 lines (55 loc) · 1.8 KB
/
EagerPriorityQueue.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 EagerPriorityQueue<T extends Comparable<T>> extends AbstractPriorityQueue<T> {
private final List<T> keys;
public EagerPriorityQueue() {
this(Comparator.naturalOrder());
}
public EagerPriorityQueue(Comparator<T> priority) {
super(priority);
keys = new ArrayList<>();
}
@Override
public int size() {
return keys.size();
}
/**
* Adds a key to {@link #keys} by the priority.
* @param key the key to be added.
*/
@Override
public void add(T key) {
// binary search (if not found, index < 0)
int index = Collections.binarySearch(keys, key, priority);
// if not found, the appropriate index is {@code -(index +1)}
if (index < 0) index = -(index + 1);
keys.add(index, key);
}
/**
* Removes the last key in {@link #keys}.
* @return the key with the highest priority if exists; otherwise, {@code null}.
*/
@Override
public T remove() {
return isEmpty() ? null : keys.remove(keys.size() - 1);
}
}