poj3083走玉米地问题

走玉米地迷宫，一般有两种简单策略，遇到岔路总是优先沿着自己的左手方向，或者右手方向走。给一个迷宫，给出这两种策略的步数，再给出最短路径的长度。

#########
#.#.#.#.#
S.......E
#.#.#.#.#
#########   迷宫示例
前两种策略用DFS的方法，最后一种用BFS的方法分别确定路线。易错点：
1.这道题目因为在走的时候遇到死路需要回头，且这个步数也要计算在内，所以不需要将走过的路设置标志。
2.总是沿着当前的左边或者右边走，即方向需要不断调整
贴代码如下：

#include<iostream>
#include<string>
#include<queue>
using namespace std;
typedef class
{
public:
    int x,y;
    int path;
}vertex;

char maze[41][41];
int trace[41][41];
int lpath,rpath,spath;
queue<vertex> bfq;

int incre[4][8]={  //first LEFT, then MID, last RIGHT
    {-1,0,0,1,1,0,0,-1},
    {0,1,1,0,0,-1,-1,0},
    {1,0,0,-1,-1,0,0,1},
    {0,-1,-1,0,0,1,1,0}
};


int LDFS(int x,int y,int ind)
{
    int nind;   
    trace[x][y]=0;
    if(maze[x][y]=='E') 
    {    
        cout<<lpath<<" ";
        return -1;
    }
    //左转
    if(maze[x+incre[ind][0]][y+incre[ind][1]]!='#'&&trace[x+incre[ind][0]][y+incre[ind][1]]==0)
    {
        lpath++;
        nind=(ind+3)%4;
        if(LDFS(x+incre[ind][0],y+incre[ind][1],nind)==-1) return -1;
    }
    //直行
    if(maze[x+incre[ind][2]][y+incre[ind][3]]!='#'&&trace[x+incre[ind][2]][y+incre[ind][3]]==0)
    {
        lpath++;
        if(LDFS(x+incre[ind][2],y+incre[ind][3],ind)==-1) return -1;
    }
    //右转
    if(maze[x+incre[ind][4]][y+incre[ind][5]]!='#'&&trace[x+incre[ind][4]][y+incre[ind][5]]==0)
    {
        lpath++;
        nind=(ind+1)%4;
        if(LDFS(x+incre[ind][4],y+incre[ind][5],nind)==-1) return -1;
    }
    //后转
    if(maze[x+incre[ind][6]][y+incre[ind][7]]!='#'&&trace[x+incre[ind][6]][y+incre[ind][7]]==0)
    {
        lpath++;
        nind=(ind+2)%4;
        if(LDFS(x+incre[ind][6],y+incre[ind][7],nind)==-1) return -1;
    }

    return lpath;
}





int RDFS(int x,int y,int ind)
{
    int nind;
       trace[x][y]=0;
    if(maze[x][y]=='E') 
    {    
        cout<<rpath<<" ";
        return -1;
    }
    //右转
    if(maze[x+incre[ind][4]][y+incre[ind][5]]!='#'&&trace[x+incre[ind][4]][y+incre[ind][5]]==0)
    {
        rpath++;
        nind=(ind+1)%4;
        if(RDFS(x+incre[ind][4],y+incre[ind][5],nind)==-1) return -1;
    }
    if(maze[x+incre[ind][2]][y+incre[ind][3]]!='#'&&trace[x+incre[ind][2]][y+incre[ind][3]]==0)
    {
        rpath++;
    
        if(RDFS(x+incre[ind][2],y+incre[ind][3],ind)==-1) return -1;
    }
    if(maze[x+incre[ind][0]][y+incre[ind][1]]!='#'&&trace[x+incre[ind][0]][y+incre[ind][1]]==0)
    {
        rpath++;
        nind=(ind+3)%4;
        if(RDFS(x+incre[ind][0],y+incre[ind][1],nind)==-1) return -1;
    }
    if(maze[x+incre[ind][6]][y+incre[ind][7]]!='#'&&trace[x+incre[ind][6]][y+incre[ind][7]]==0)
    {
        rpath++;
        nind=(ind+2)%4;
        if(RDFS(x+incre[ind][6],y+incre[ind][7],nind)==-1) return -1;
    }
    return rpath;
}

void BFS(vertex v,int ind)
{
    vertex a,b;
    bfq.push(v);
    trace[v.x][v.y]=1;
    while(bfq.size()!=0)
    {
        a=bfq.front();
        bfq.pop();
        if(maze[a.x+incre[ind][4]][a.y+incre[ind][5]]!='#'&&trace[a.x+incre[ind][4]][a.y+incre[ind][5]]==0)
        {
            trace[a.x+incre[ind][4]][a.y+incre[ind][5]]=1;
            b.x=a.x+incre[ind][4];   b.y=a.y+incre[ind][5];   b.path=a.path+1;
            if(maze[b.x][b.y]=='E')
            {
                cout<<b.path<<endl;
                break;
            }
            bfq.push(b);
        }
        if(maze[a.x+incre[ind][2]][a.y+incre[ind][3]]!='#'&&trace[a.x+incre[ind][2]][a.y+incre[ind][3]]==0)
        {
            trace[a.x+incre[ind][2]][a.y+incre[ind][3]]=1;
            b.x=a.x+incre[ind][2];   b.y=a.y+incre[ind][3];   b.path=a.path+1;
            if(maze[b.x][b.y]=='E')
            {
                cout<<b.path<<endl;
                break;
            }            
            bfq.push(b);            
        }
        if(maze[a.x+incre[ind][0]][a.y+incre[ind][1]]!='#'&&trace[a.x+incre[ind][0]][a.y+incre[ind][1]]==0)
        {
            trace[a.x+incre[ind][0]][a.y+incre[ind][1]]=1;
            b.x=a.x+incre[ind][0];   b.y=a.y+incre[ind][1];   b.path=a.path+1;
            if(maze[b.x][b.y]=='E')
            {
                cout<<b.path<<endl;
                break;
            }
            bfq.push(b);        
        }
        if(maze[a.x+incre[ind][6]][a.y+incre[ind][7]]!='#'&&trace[a.x+incre[ind][6]][a.y+incre[ind][7]]==0)
        {
            trace[a.x+incre[ind][6]][a.y+incre[ind][7]]=1;
            b.x=a.x+incre[ind][6];   b.y=a.y+incre[ind][7];   b.path=a.path+1;
            if(maze[b.x][b.y]=='E')
            {
                cout<<b.path<<endl;
                break;
            }
            bfq.push(b);        
        }
    }
}
        

    
    


int main()
{
    int instan,w,h,i,j,sx,sy,ind;
    char in;
    cin>>instan;
    for(int Num=0;Num<instan;Num++)
    {
        cin>>w>>h;
        for(i=0;i<h;i++)
            for(j=0;j<w;j++)
            {
                cin>>in;
                maze[i][j]=in;
                if(maze[i][j]=='S')
                {
                    sx=i;sy=j;
                }
            }
        if(sy==0) ind=0;
        if(sx==0) ind=1;
        if(sy==(w-1)) ind=2;
        if(sx==(h-1)) ind=3;
        lpath=1;
        memset(trace,0,sizeof(trace));
        lpath=LDFS(sx,sy,ind);
        rpath=1,spath=1;
        memset(trace,0,sizeof(trace));
        rpath=RDFS(sx,sy,ind);
        //cout<<lpath<<" "<<rpath<<endl;
        vertex vs;
        vs.x=sx;vs.y=sy;vs.path=1;
        memset(trace,0,sizeof(trace));
        BFS(vs,ind);
        while(bfq.empty()!=1)
        {
            bfq.pop();
        }
    }
    return 0;
}