72 lines
2.1 KiB
C
72 lines
2.1 KiB
C
/*
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* A* Search - A search library used in Empire to determine paths between
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* objects.
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* Copyright (C) 1990-1998 Phil Lapsley
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include "as.h"
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/*
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* Extend the queue by neighbors. This entails getting the
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* coordinates of all the neighbors, figuring out their lower bound
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* costs, throwing away ones that are more expensive than ones we
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* already have, sorting, tand then merging into the queue.
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*/
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struct as_queue *
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as_extend(struct as_data *adp)
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{
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struct as_queue *qp;
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int i;
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struct as_queue *head;
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head = adp->head;
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/* Find the neighboring coordinates. */
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i = adp->neighbor(head->np->c, adp->neighbor_coords, adp->userdata);
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if (i == 0)
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return NULL;
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/*
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* Get rid of neighbors that are more costly than ones we already have,
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* and sort the rest into an array of as_nodes.
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*/
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i = as_winnow(adp, adp->neighbor_coords, i);
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if (i < 0)
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return NULL;
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if (i > 1)
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qsort(adp->neighbor_nodes, i,
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sizeof(*adp->neighbor_nodes), as_costcomp);
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/* remove old coord from head of queue and add to list of tried */
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qp = head;
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head = head->next;
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if (head)
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head->prev = NULL;
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if (adp->tried) {
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adp->tried->prev = qp;
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qp->next = adp->tried;
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adp->tried = qp;
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} else
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adp->tried = qp;
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adp->tried->np->flags |= AS_TRIED;
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head = as_merge(adp, head, adp->neighbor_nodes);
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return head;
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}
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