B星算法的原理图:
以下是C语言的一段源码
#ifndef __ASTARPATHFINDER_H__ #define __ASTARPATHFINDER_H__ #include "cocos2d.h" USING_NS_CC; /** * 横向移动一格的路径评分 */ static const int COST_HORIZONTAL = 20; /** * 竖向移动一格的路径评分 */ static const int COST_VERTICAL = 5; /** * 斜向移动一格的路径评分 */ static const int COST_DIAGONAL = 12; class PathInfo; /** * A星寻路类 * @author hpking * */ class AStarPathFinder { // 未探索的节点列表 cocos2d::CCArray* _openSteps; // 已探索的,不需要再寻路的节点列表 cocos2d::CCArray* _closedSteps; // 地图相关数据 PathInfo* _pathInfo; public: AStarPathFinder(PathInfo* info); virtual ~AStarPathFinder(); /** * public 寻路 * * @param CCPoint startPoint tile开始坐标点 * @param CCPoint endPoint tile结束坐标点 * @return CCArray* 读取方法:CCPointFromString ( string->getCString() ) */ CCArray* find( CCPoint startTilePt, CCPoint endTilePt ); private: // 最短路径步数 class ShortestPathStep : public cocos2d::CCObject { public: bool initWithPosition( cocos2d::CCPoint pos ) { bool bRet = false; do { position = pos; gScore = 0; hScore = 0; parent = NULL; inOpen = false; inClose = false; bRet = true; } while ( 0 ); return bRet; } int fScore() { return this->getGScore() + this->getHScore(); } inline bool operator==( const ShortestPathStep* other ) { return isEqual( other ); } bool isEqual( const ShortestPathStep* other ) { return this->getPosition().equals ( other->getPosition() ); } static ShortestPathStep* inst( cocos2d::CCPoint pos ) { AStarPathFinder::ShortestPathStep* sps = new AStarPathFinder::ShortestPathStep; if ( sps && sps->initWithPosition ( pos ) ) { sps->autorelease(); return sps; } CC_SAFE_DELETE ( sps ); return NULL; } CC_SYNTHESIZE( cocos2d::CCPoint, position, Position ); CC_SYNTHESIZE( int, gScore, GScore ); CC_SYNTHESIZE( int, hScore, HScore ); CC_SYNTHESIZE( ShortestPathStep*, parent, Parent ); CC_SYNTHESIZE( bool, inOpen, InOpen ); CC_SYNTHESIZE( bool, inClose, InClose ); private: cocos2d::CCString* description() { return CCString::createWithFormat ( "pos = [%f, %f], g=%d, h=%d, f=%d", this->getPosition().x, this->getPosition().y, this->getGScore(), this->getHScore(), this->fScore() ); } }; private: void destroyLists(); CCArray* createPath( ShortestPathStep* step );//int xStart, int yStart void findAndSort( ShortestPathStep* step ); void insertAndSort( ShortestPathStep* step ); /** * private 判断是否超出边界或路点是否可走 * * @param CCPoint tpt * @return bool */ bool isWalkable( CCPoint tpt ); /** * private 计算G值 * * @param Node * curNode * @param Node * node * @return int */ int getGValue( ShortestPathStep* curStep, ShortestPathStep* step ); /** * private 计算H值 * * @param Node * curNode * @param Node * endNode * @param Node * node * @return int */ int getHValue( ShortestPathStep* curStep, ShortestPathStep* endStep, ShortestPathStep* step ); cocos2d::CCArray* getAroundsNode( CCPoint tPt ); bool isInClosed(CCPoint tPt); void setOpenSteps ( cocos2d::CCArray* var ); void setClosedSteps ( cocos2d::CCArray* var ); void setShortestPath ( cocos2d::CCArray* var ); }; #endif
#include "AStarPathFinder.h" #include "map/PathInfo.h" AStarPathFinder::AStarPathFinder( PathInfo* info ) { _pathInfo = info; _openSteps = NULL; _closedSteps = NULL; } AStarPathFinder::~AStarPathFinder() { destroyLists(); } // 获取毫秒时间 long msNow() { struct cc_timeval now; CCTime::gettimeofdayCocos2d( &now, NULL ); return ( now.tv_sec * 1000 + now.tv_usec / 1000 ); } CCArray* AStarPathFinder::find( CCPoint startTilePt, CCPoint endTilePt ) { bool isFinded = false; //能否找到路径,true-已找到 // 到达终点 if ( startTilePt.equals ( endTilePt ) ) { CCLog ( "You're already there! :P" ); return NULL; } // 终点不可走,直接退出(可优化为最近的可走地点停止) if ( !isWalkable( endTilePt ) ) { CCLog ( "blocked! :P" ); return NULL; } // 设置打开和封闭步数 setOpenSteps ( CCArray::create() ); setClosedSteps ( CCArray::create() ); //CCLog ( "From:(%f, %f) To(%f, %f)", startTilePt.x, startTilePt.y, endTilePt.x, endTilePt.y ); // 结束坐标 ShortestPathStep* endStep = ShortestPathStep::inst ( endTilePt ); // 插入开始点 insertAndSort ( ShortestPathStep::inst ( startTilePt ) ); ShortestPathStep* curStep; long time1 = msNow(); do { // 取出并删除开放列表第一个元素 curStep = ( ShortestPathStep* ) _openSteps->objectAtIndex ( 0 ); curStep->setInClose( true ); curStep->setInOpen( false ); _closedSteps->addObject ( curStep ); _openSteps->removeObjectAtIndex ( 0 ); // 当前节点==目标节点 if ( curStep->getPosition().equals( endTilePt ) ) { isFinded = true; //能达到终点,找到路径 break; } // 取相邻八个方向的节点,去除不可通过和已在关闭列表中的节点 CCArray* aroundNodes = getAroundsNode ( curStep->getPosition() ); //CCLog("8 dirc %d",aroundNodes->count()); CCObject* obj; CCARRAY_FOREACH ( aroundNodes, obj ) { // 计算 G, H 值 CCString* string = ( CCString* ) obj; ShortestPathStep* nextStep = new ShortestPathStep; nextStep->initWithPosition ( CCPointFromString ( string->getCString() ) ); int g = getGValue ( curStep , nextStep ); int h = getHValue ( curStep , endStep , nextStep ); if ( nextStep->getInOpen() ) // 如果节点已在播放列表中 { // 如果该节点新的G值比原来的G值小,修改F,G值,设置该节点的父节点为当前节点 if ( g < nextStep->getGScore() ) { nextStep->setGScore( g ); nextStep->setHScore( h ); nextStep->setParent( curStep ); findAndSort ( nextStep ); nextStep->release(); } } else // 如果节点不在开放列表中 { // 插入开放列表中,并按照估价值排序 nextStep->setGScore( g ); nextStep->setHScore( h ); nextStep->setParent( curStep ); insertAndSort ( nextStep ); nextStep->release(); } //CCLog("open num:%d",_openSteps->count()); } } while ( _openSteps->count() > 0 ); CCLog( "a* time:%d", msNow() - time1 ); /*if( _openSteps ) CCLog( "finded:%d, openlen %d, closelen %d", isFinded ? 1 : 0, _openSteps->count(), _closedSteps->count() );*/ // 找到路径 if ( isFinded ) { CCArray* path = createPath ( curStep ); destroyLists (); return path; } else // 没有找到路径 { destroyLists (); return NULL; } } void AStarPathFinder::destroyLists() { CC_SAFE_RELEASE_NULL ( _openSteps ); CC_SAFE_RELEASE_NULL ( _closedSteps ); } CCArray* AStarPathFinder::createPath( ShortestPathStep* step )//int xStart, int yStart { CCArray* path = CCArray::create(); CCString* str; do { if ( step->getParent() != NULL ) { str = CCString::createWithFormat ( "{%f, %f}", step->getPosition().x, step->getPosition().y ); path->insertObject ( str, 0 ); } step = step->getParent(); } while ( step != NULL ); return path; } void AStarPathFinder::findAndSort( ShortestPathStep* step ) { unsigned int count = _openSteps->count(); if ( count < 1 ) return; int stepFScore = step->fScore(); for ( unsigned int i = 0; i < count; i++ ) { ShortestPathStep* sps = ( ShortestPathStep* ) _openSteps->objectAtIndex ( i ); if ( stepFScore <= sps->fScore() ) _openSteps->insertObject ( step, i ); if ( step->getPosition().equals( sps->getPosition() ) ) _openSteps->removeObjectAtIndex( i ); } } void AStarPathFinder::insertAndSort( ShortestPathStep* step ) { step->setInOpen( true ); int stepFScore = step->fScore(); unsigned int count = _openSteps->count(); if( count == 0 ) _openSteps->addObject( step ); else { for ( unsigned int i = 0; i < count; i++ ) { ShortestPathStep* sps = ( ShortestPathStep* ) _openSteps->objectAtIndex ( i ); if ( stepFScore <= sps->fScore() ) { _openSteps->insertObject ( step, i ); return; } } } } bool AStarPathFinder::isWalkable( CCPoint tPt ) { // 1. 是否是有效的地图上点(数组边界检查) if ( tPt.x < _pathInfo->startPt.x || tPt.x >= _pathInfo->iCol ) return false; if ( tPt.y < _pathInfo->startPt.y || tPt.y >= _pathInfo->iRow ) return false; // 2. 是否是walkable return _pathInfo->isWalkable( tPt ); } /** * private 计算G值 * * @param ShortestPathStep * curStep * @param ShortestPathStep * step * @return int */ int AStarPathFinder::getGValue( ShortestPathStep* curStep, ShortestPathStep* step ) { int g = 0; if ( curStep->getPosition().y == step->getPosition().y ) // 横向 左右 { g = curStep->getGScore() + COST_HORIZONTAL; } else if ( curStep->getPosition().y + 2 == step->getPosition().y || curStep->getPosition().y - 2 == step->getPosition().y ) // 竖向 上下 { g = curStep->getGScore() + COST_VERTICAL * 2; } else // 斜向 左上 左下 右上 右下 { g = curStep->getGScore() + COST_DIAGONAL; } return g; } /** * private 计算H值 * * @param ShortestPathStep * curStep * @param ShortestPathStep * endStep * @param ShortestPathStep * step * @return int */ int AStarPathFinder::getHValue( ShortestPathStep* curStep, ShortestPathStep* endStep, ShortestPathStep* step ) { if ( curStep == NULL || endStep == NULL || step == NULL ) return 0; // 节点到0,0点的x轴距离 int to0 = step->getPosition().x * COST_HORIZONTAL + ( ( int )step->getPosition().y & 1 ) * COST_HORIZONTAL / 2; // 终止节点到0,0点的x轴距离 int endTo0 = endStep->getPosition().x * COST_HORIZONTAL + ( ( int )endStep->getPosition().y & 1 ) * COST_HORIZONTAL / 2; return abs ( ( float )endTo0 - ( float )to0 ) + abs ( ( float )endStep->getPosition().y - ( float )step->getPosition().y ) * COST_VERTICAL; } cocos2d::CCArray* AStarPathFinder::getAroundsNode( CCPoint tPt ) { CCArray* aroundNodes = CCArray::create(); /// 菱形组合的地图八方向与正常不同 // 左 CCPoint p = CCPointMake ( tPt.x - 1, tPt.y ); CCString* str; if ( isWalkable ( p ) && !isInClosed( p ) ) // 可走并且不在关闭列表 { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "left=%s", str->getCString() ); aroundNodes->addObject ( str ); } // 右 p = CCPointMake ( tPt.x + 1, tPt.y ); if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); // CCLOG( "right=%s", str->getCString() ); aroundNodes->addObject ( str ); } // 上 p = CCPointMake ( tPt.x, tPt.y - 2 ); // -2 if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "up=%s", str->getCString() ); aroundNodes->addObject ( str ); } // 下 p = CCPointMake ( tPt.x, tPt.y + 2 );// + 2 if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "down=%s", str->getCString() ); aroundNodes->addObject ( str ); } // 左上 p = CCPointMake ( tPt.x - 1 + ( ( int )tPt.y & 1 ), tPt.y - 1 ); if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "leftUp=%s", str->getCString() ); aroundNodes->addObject ( str ); } // 左下 p = CCPointMake ( tPt.x - 1 + ( ( int )tPt.y & 1 ), tPt.y + 1 ); if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "leftDown=%s", str->getCString() ); aroundNodes->addObject ( str ); } //右上 p = CCPointMake ( tPt.x + ( ( int )tPt.y & 1 ), tPt.y - 1 ); if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "rightUp=%s", str->getCString() ); aroundNodes->addObject ( str ); } //右下 p = CCPointMake ( tPt.x + ( ( int )tPt.y & 1 ), tPt.y + 1 ); if ( isWalkable ( p ) && !isInClosed( p ) ) { str = CCString::createWithFormat ( "{%f, %f}", p.x, p.y ); //CCLOG( "rightDown=%s", str->getCString() ); aroundNodes->addObject ( str ); } return aroundNodes; } bool AStarPathFinder::isInClosed( CCPoint pt ) { CCObject* temp; CCARRAY_FOREACH ( _closedSteps, temp ) { ShortestPathStep* sps = ( ShortestPathStep* ) temp; if( sps->getPosition().equals( pt ) ) { return true; } } return false; } void AStarPathFinder::setOpenSteps ( cocos2d::CCArray* var ) { if ( _openSteps != var ) { CC_SAFE_RELEASE_NULL ( _openSteps ); CC_SAFE_RETAIN ( var ); _openSteps = var; } } void AStarPathFinder::setClosedSteps ( cocos2d::CCArray* var ) { if ( _closedSteps != var ) { CC_SAFE_RELEASE_NULL ( _closedSteps ); CC_SAFE_RETAIN ( var ); _closedSteps = var; } } void AStarPathFinder::setShortestPath ( cocos2d::CCArray* var ) { /*if ( shortestPath != var ) { CC_SAFE_RELEASE_NULL ( shortestPath ); CC_SAFE_RETAIN ( var ); shortestPath = var; }*/ }
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为此我做了一个各种算法时间的效率对比
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关于B星和B星算法的加强版C星算法的使用,强调的是速度而不是种类繁多的花样。
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言归正传,以下我做了一些测试工具(仅仅是测试)