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133 lines
3.2 KiB
C++
133 lines
3.2 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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*
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* Based on the original sources
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* Faery Tale II -- The Halls of the Dead
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* (c) 1993-1996 The Wyrmkeep Entertainment Co.
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*/
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#ifndef SAGA2_PRIQUEUE_H
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#define SAGA2_PRIQUEUE_H
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namespace Saga2 {
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template <class ITEM, int size>
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class PriorityQueue {
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int16 tail; // end index of queue
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ITEM queue[size + 1];
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static int16 parentIndex(int16 index) {
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return index >> 1;
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}
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static int16 child1Index(int16 index) {
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return index << 1;
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}
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static int16 child2Index(int16 index) {
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return (index >> 1) + 1;
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}
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public:
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PriorityQueue(void) { // constructor
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tail = 1;
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}
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bool insert(ITEM &newItem); // insert an item
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bool remove(ITEM &result); // remove an item
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void clear(void) {
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tail = 1; // clear the queue
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}
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int16 getCount(void) {
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return tail - 1;
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}
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};
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// Function to insert an element into the queue
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template <class ITEM, int size>
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bool PriorityQueue<ITEM, size>::insert(ITEM &newItem) {
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int16 index,
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parentIndex,
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newVal = (int)newItem;
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ITEM *qi,
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*parentItem;
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if (tail >= size + 1) return false;
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for (index = tail, qi = &queue[index];
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index > 1;
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index = parentIndex, qi = parentItem) {
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parentIndex = PriorityQueue::parentIndex(index);
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parentItem = &queue[parentIndex];
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if ((int)*parentItem <= newVal) break;
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*qi = *parentItem;
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}
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*qi = newItem;
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tail++;
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return true;
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}
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// Function to remove the lowest element from the queue
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template <class ITEM, int size>
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bool PriorityQueue<ITEM, size>::remove(ITEM &result) {
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ITEM *item = &queue[1],
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*child;
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int16 itemNum = 1,
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childNum,
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tailVal;
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if (tail <= 1) return false;
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result = *item;
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tail--;
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tailVal = (int)queue[tail];
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for (;;) {
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childNum = child1Index(itemNum);
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if (childNum >= tail) break;
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child = &queue[childNum];
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// Select the lowest of the two children
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if (childNum + 1 < tail
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&& (int)child[0] > (int)child[1]) {
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childNum++;
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child++;
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}
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if ((int)*child >= tailVal) break;
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*item = *child;
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item = child;
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itemNum = childNum;
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}
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if (itemNum != tail) {
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*item = queue[tail];
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}
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return true;
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}
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} // end of namepsace Saga2
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#endif
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