JAVA 树中按最长路径行驶_java 获取树最长路径-优快云博客

本文链接：https://blog.youkuaiyun.com/xuricai/article/details/222720

这个方法用于寻找给定位置和方向下，树中的最长路径。它通过递归检查上下左右四个方向，记录并返回最长路径的Vector。如果当前位置没有可行路径，则返回null。

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private Vector findRoad(int posX,int posY,int dir){
        Vector roadUPVec=null,roadRIGHTVec=null,roadDOWNVec=null,roadLEFTVec=null;
        boolean tempUP=false,tempRIGHT=false,tempLEFT=false,tempDOWN=false;
        int upNum=0,downNum=0,rightNum=0,leftNum=0,maxNum=0;

        if(posY>0 && m_nowMap[posX][posY-1]!=0 && dir!=DIR_UP){
            roadUPVec=new Vector();
            roadUPVec.addElement(new Integer(posX));
            roadUPVec.addElement(new Integer(posY-1));
            Vector tempVec=findRoad(posX,posY-1,DIR_DOWN);
            if(tempVec!=null){
                for(int i=0;i<tempVec.size();i++)
                    roadUPVec.addElement(tempVec.elementAt(i));
            }
        }
        else
            tempUP=false;
        if(posX<COLUMN-1 && m_nowMap[posX+1][posY]!=0 && dir!=DIR_RIGHT){
            roadRIGHTVec=new Vector();
            roadRIGHTVec.addElement(new Integer(posX+1));
            roadRIGHTVec.addElement(new Integer(posY));
            Vector tempVec=findRoad(posX+1,posY,DIR_LEFT);
            if(tempVec!=null){
                for(int i=0;i<tempVec.size();i++)
                    roadRIGHTVec.addElement(tempVec.elementAt(i));
            }
        }
        else
            tempRIGHT=false;
        if(posY<ROW && m_nowMap[posX][posY+1]!=0 && dir!=DIR_DOWN){
            roadDOWNVec=new Vector();
            roadDOWNVec.addElement(new Integer(posX));
            roadDOWNVec.addElement(new Integer(posY+1));
            Vector tempVec=findRoad(posX,posY+1,DIR_UP);
            if(tempVec!=null){
                for(int i=0;i<tempVec.size();i++)
                    roadDOWNVec.addElement(tempVec.elementAt(i));
            }
        }
        else
            tempDOWN=false;
        if(posX<0 && m_nowMap[posX-1][posY]!=0 && dir!=DIR_LEFT){
            roadLEFTVec=new Vector();
            roadLEFTVec.addElement(new Integer(posX-1));
            roadLEFTVec.addElement(new Integer(posY));
            Vector tempVec=findRoad(posX-1,posY,DIR_RIGHT);
            if(tempVec!=null){
                for(int i=0;i<tempVec.size();i++)
                    roadLEFTVec.addElement(tempVec.elementAt(i));
            }
        }
        else
            tempLEFT=false;
        if(!tempUP && !tempRIGHT && !tempDOWN && !tempLEFT)
            return null;
        else{
            if(roadUPVec!=null)
                upNum=roadUPVec.size();
            if(roadRIGHTVec!=null)
                rightNum=roadUPVec.size();
            if(roadDOWNVec!=null)
                downNum=roadUPVec.size();
            if(roadLEFTVec!=null)
                leftNum=roadUPVec.size();
            maxNum=rightNum;
            if(upNum>maxNum)
                maxNum=upNum;
            if(leftNum>maxNum)
                maxNum=leftNum;
            if(downNum>maxNum)
                maxNum=downNum;

            if(maxNum==upNum)
                return roadUPVec;
            else
            if(maxNum==downNum)
                return roadDOWNVec;
            else
            if(maxNum==rightNum)
                return roadRIGHTVec;
            else
            if(maxNum==leftNum)
                return roadLEFTVec;
            else
                return null;
        }
    }