使用Java编写的B*算法
package rpg.stage.path; import java.util.ArrayList; import java.util.HashSet; import java.util.Iterator; import rpg.objs.Point; public class BFinding { public BFinding() { } protected HashSet<Point> openList = new HashSet<Point>(); protected HashSet<Point> leftList = new HashSet<Point>(); protected HashSet<Point> rightList = new HashSet<Point>(); protected HashSet<Point> closeList = new HashSet<Point>(); public synchronized ArrayList<int[]> find(Point start,Point end,boolean canPenetrate){ if(end == null){ return new ArrayList<int[]>(); } if(start == null){ return new ArrayList<int[]>(); } end.clear(); start.clear(); openList.clear(); openList.add(start); leftList.clear(); rightList.clear(); closeList.clear(); int count = 0; while(!openList.isEmpty() || !leftList.isEmpty() || !rightList.isEmpty()){ count ++; if(count>1000) break; Iterator<Point> it = openList.iterator(); if(it.hasNext()){ Point p = it.next(); it.remove(); if(sideNext(p,end,0,canPenetrate))break; } it = leftList.iterator(); if(it.hasNext()){ Point p = it.next(); it.remove(); if(sideNext(p,end,1,canPenetrate))break; } it = rightList.iterator(); if(it.hasNext()){ Point p = it.next(); it.remove(); if(sideNext(p,end,-1,canPenetrate))break; } } final ArrayList<int[]> list = new ArrayList<int[]>(); while(end.parent!=null){ list.add(0,new int[]{end.x,end.y}); end = end.parent; } return list; } /** * * @param p * @param end 目标点 * @param side 0 direct -1 right 1 left * @param canPenetrate 可否穿透 */ protected boolean sideNext(Point p,Point end,int side,boolean canPenetrate){ int dir = Point.getDirSimple(p, end); Point nextp = null; if(closeList.contains(p)){ nextp = nextPassPointSide(p,end,-1,canPenetrate); if(nextp != null){ if(nextp == end){ nextp.parent = p; return true; } if(this.closeList.contains(nextp)) // return sideNext(nextp, end, side, canPenetrate); return false; else if(!this.leftList.contains(nextp)) addToSearch(p,nextp,this.rightList); } nextp = nextPassPointSide(p,end,1,canPenetrate); if(nextp != null){ if(nextp == end){ nextp.parent = p; return true; } if(this.closeList.contains(nextp)) // return sideNext(nextp, end, side, canPenetrate); return false; else if(!this.rightList.contains(nextp)) addToSearch(p,nextp,this.leftList); } return false; } this.closeList.add(p); if(side == 0){ if(p.canWalkDir(dir,canPenetrate)){//下一个点可以走 nextp = p.getPassPointByDir(dir); if(nextp == end){ nextp.parent = p; return true; } if(!this.closeList.contains(nextp)){ addToSearch(p,nextp,this.openList); } } else//不可走,就分支出两个围绕探索点 { nextp = nextPassPointSide(p,end,-1,canPenetrate); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null){ if(this.closeList.contains(nextp)) return sideNext(nextp, end, side, canPenetrate); // return false; else if(!this.leftList.contains(nextp)) addToSearch(p,nextp,this.rightList); } nextp = nextPassPointSide(p,end,1,canPenetrate); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null){ if(this.closeList.contains(nextp)) return sideNext(nextp, end, side, canPenetrate); // return false; else if(!this.rightList.contains(nextp)) addToSearch(p,nextp,this.leftList); } } } else if(side>0){ nextp = p.getPassPointByDir(dir); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null && !this.closeList.contains(nextp)){ addToSearch(p,nextp,this.openList); } else { nextp = nextPassPointSide(p,end,1,canPenetrate); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null && !this.closeList.contains(nextp) && !this.rightList.contains(nextp)){ addToSearch(p,nextp,this.leftList); } } } else if(side<0){ nextp = p.getPassPointByDir(dir); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null && !this.closeList.contains(nextp)){ addToSearch(p,nextp,this.openList); } else { nextp = nextPassPointSide(p,end,-1,canPenetrate); if(nextp == end){ nextp.parent = p; return true; } if(nextp != null && !this.closeList.contains(nextp) && !this.leftList.contains(nextp)){ addToSearch(p,nextp,this.rightList); } } } return false; } protected void addToSearch(Point parent,Point next,HashSet<Point> list){ next.clear(); next.parent = parent; list.add(next); } /** * * @param p * @param side >0 或者 <0 * @param canPenetrate * @return */ protected Point nextPassPointSide(Point p,Point end,int side,boolean canPenetrate){ int dir = Point.getDirSimple(p, end); Point nextp = null; if(side<0){ while(side>=-7){ dir = Point.rightdir(dir); if(p.canWalkDir(dir,canPenetrate)){ nextp = p.getPassPointByDir(dir); if(!this.closeList.contains(nextp)){ break; } } side--; } } else { while(side<=7){ dir = Point.leftdir(dir); if(p.canWalkDir(dir,canPenetrate)){ nextp = p.getPassPointByDir(dir); if(!this.closeList.contains(nextp)){ break; } } side++; } } return nextp; } }