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

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

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

     return lpath;
 }

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

         if(RDFS(x+incre[ind][],y+incre[ind][],ind)==-) return -;
     }
     if(maze[x+incre[ind][]][y+incre[ind][]]!='#'&&trace[x+incre[ind][]][y+incre[ind][]]==)
     {
         rpath++;
         nind=(ind+)%;
         if(RDFS(x+incre[ind][],y+incre[ind][],nind)==-) return -;
     }
     if(maze[x+incre[ind][]][y+incre[ind][]]!='#'&&trace[x+incre[ind][]][y+incre[ind][]]==)
     {
         rpath++;
         nind=(ind+)%;
         if(RDFS(x+incre[ind][],y+incre[ind][],nind)==-) return -;
     }
     return rpath;
 }

 void BFS(vertex v,int ind)
 {
     vertex a,b;
     bfq.push(v);
     trace[v.x][v.y]=;
     while(bfq.size()!=)
     {
         a=bfq.front();
         bfq.pop();
         if(maze[a.x+incre[ind][]][a.y+incre[ind][]]!='#'&&trace[a.x+incre[ind][]][a.y+incre[ind][]]==)
         {
             trace[a.x+incre[ind][]][a.y+incre[ind][]]=;
             b.x=a.x+incre[ind][];   b.y=a.y+incre[ind][];   b.path=a.path+;
             if(maze[b.x][b.y]=='E')
             {
                 cout<<b.path<<endl;
                 break;
             }
             bfq.push(b);
         }
         if(maze[a.x+incre[ind][]][a.y+incre[ind][]]!='#'&&trace[a.x+incre[ind][]][a.y+incre[ind][]]==)
         {
             trace[a.x+incre[ind][]][a.y+incre[ind][]]=;
             b.x=a.x+incre[ind][];   b.y=a.y+incre[ind][];   b.path=a.path+;
             if(maze[b.x][b.y]=='E')
             {
                 cout<<b.path<<endl;
                 break;
             }
             bfq.push(b);
         }
         if(maze[a.x+incre[ind][]][a.y+incre[ind][]]!='#'&&trace[a.x+incre[ind][]][a.y+incre[ind][]]==)
         {
             trace[a.x+incre[ind][]][a.y+incre[ind][]]=;
             b.x=a.x+incre[ind][];   b.y=a.y+incre[ind][];   b.path=a.path+;
             if(maze[b.x][b.y]=='E')
             {
                 cout<<b.path<<endl;
                 break;
             }
             bfq.push(b);
         }
         if(maze[a.x+incre[ind][]][a.y+incre[ind][]]!='#'&&trace[a.x+incre[ind][]][a.y+incre[ind][]]==)
         {
             trace[a.x+incre[ind][]][a.y+incre[ind][]]=;
             b.x=a.x+incre[ind][];   b.y=a.y+incre[ind][];   b.path=a.path+;
             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=;Num<instan;Num++)
     {
         cin>>w>>h;
         for(i=;i<h;i++)
             for(j=;j<w;j++)
             {
                 cin>>in;
                 maze[i][j]=in;
                 if(maze[i][j]=='S')
                 {
                     sx=i;sy=j;
                 }
             }
         if(sy==) ind=;
         if(sx==) ind=;
         if(sy==(w-)) ind=;
         if(sx==(h-)) ind=;
         lpath=;
         memset(trace,,sizeof(trace));
         lpath=LDFS(sx,sy,ind);
         rpath=,spath=;
         memset(trace,,sizeof(trace));
         rpath=RDFS(sx,sy,ind);
         //cout<<lpath<<" "<<rpath<<endl;
         vertex vs;
         vs.x=sx;vs.y=sy;vs.path=;
         memset(trace,,sizeof(trace));
         BFS(vs,ind);
         while(bfq.empty()!=)
         {
             bfq.pop();
         }
     }
     return ;
 }