/******************************************************************************* * Copyright (c) 2015 * * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. *******************************************************************************/ package jsettlers.algorithms.path.astar.queues.bucket; import jsettlers.common.utils.collections.list.DoubleLinkedIntListItem; import jsettlers.common.utils.collections.list.DoubleLinkedList; /** * This class implements a minimum bucket priority queue with double liked lists. * <p /> * {@link #insert(int, float)}, {@link #increasedPriority(int, float, float)}, {@link #size()} and {@link #isEmpty()} are in O(1)<br> * {@link #clear()} and {@link #deleteMin()} are in O({@link #NUMBER_OF_BUCKETS}) = O({@value #NUMBER_OF_BUCKETS}) that's actually a constant value. * * @author Andreas Eberle * */ public final class ListMinBucketQueue extends AbstractBucketQueue { /** * NOTE: The number of buckets MUST BE a power of 2!! */ public static final int NUMBER_OF_BUCKETS = 4; private static final int MODULO_MASK = NUMBER_OF_BUCKETS - 1; private final DoubleLinkedList<DoubleLinkedIntListItem>[] buckets; private final DoubleLinkedIntListItem[] handles; private int minIdx = 0; private int size = 0; public ListMinBucketQueue(int maxNumberOfIds) { this.buckets = DoubleLinkedList.getArray(NUMBER_OF_BUCKETS); this.handles = new DoubleLinkedIntListItem[maxNumberOfIds]; for (int i = 0; i < maxNumberOfIds; i++) { handles[i] = new DoubleLinkedIntListItem(i); } } @Override public void insert(int elementId, float rank) { buckets[getRankIdx(rank)].pushFront(handles[elementId]); size++; } private static final int getRankIdx(float rank) { return ((int) rank) & MODULO_MASK; } @Override public int size() { return size; } private final void remove(int elementId, int rankIdx) { buckets[rankIdx].remove(handles[elementId]); size--; } @Override public void clear() { for (int i = 0; i < NUMBER_OF_BUCKETS; i++) { this.buckets[i].clear(); } size = 0; } @Override public int deleteMin() { while (buckets[minIdx].isEmpty()) { minIdx = (minIdx + 1) & MODULO_MASK; } size--; final int elementId = buckets[minIdx].popFront().value; return elementId; } @Override public void increasedPriority(int elementId, float oldRank, float newRank) { remove(elementId, getRankIdx(oldRank)); insert(elementId, newRank); } @Override public boolean isEmpty() { return size == 0; } }