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：

  1 #include<iostream>
  2 #include<string>
  3 #include<queue>
  4 using namespace std;
  5 typedef class
  6 {
  7 public:
  8     int x,y;
  9     int path;
 10 }vertex;
 11 
 12 char maze[41][41];
 13 int trace[41][41];
 14 int lpath,rpath,spath;
 15 queue<vertex> bfq;
 16 
 17 int incre[4][8]={  //first LEFT, then MID, last RIGHT
 18     {-1,0,0,1,1,0,0,-1},
 19     {0,1,1,0,0,-1,-1,0},
 20     {1,0,0,-1,-1,0,0,1},
 21     {0,-1,-1,0,0,1,1,0}
 22 };
 23 
 24 
 25 int LDFS(int x,int y,int ind)
 26 {
 27     int nind;   
 28     trace[x][y]=0;
 29     if(maze[x][y]=='E') 
 30     {    
 31         cout<<lpath<<" ";
 32         return -1;
 33     }
 34     //左转
 35     if(maze[x+incre[ind][0]][y+incre[ind][1]]!='#'&&trace[x+incre[ind][0]][y+incre[ind][1]]==0)
 36     {
 37         lpath++;
 38         nind=(ind+3)%4;
 39         if(LDFS(x+incre[ind][0],y+incre[ind][1],nind)==-1) return -1;
 40     }
 41     //直行
 42     if(maze[x+incre[ind][2]][y+incre[ind][3]]!='#'&&trace[x+incre[ind][2]][y+incre[ind][3]]==0)
 43     {
 44         lpath++;
 45         if(LDFS(x+incre[ind][2],y+incre[ind][3],ind)==-1) return -1;
 46     }
 47     //右转
 48     if(maze[x+incre[ind][4]][y+incre[ind][5]]!='#'&&trace[x+incre[ind][4]][y+incre[ind][5]]==0)
 49     {
 50         lpath++;
 51         nind=(ind+1)%4;
 52         if(LDFS(x+incre[ind][4],y+incre[ind][5],nind)==-1) return -1;
 53     }
 54     //后转
 55     if(maze[x+incre[ind][6]][y+incre[ind][7]]!='#'&&trace[x+incre[ind][6]][y+incre[ind][7]]==0)
 56     {
 57         lpath++;
 58         nind=(ind+2)%4;
 59         if(LDFS(x+incre[ind][6],y+incre[ind][7],nind)==-1) return -1;
 60     }
 61 
 62     return lpath;
 63 }
 64 
 65 
 66 
 67 
 68 
 69 int RDFS(int x,int y,int ind)
 70 {
 71     int nind;
 72        trace[x][y]=0;
 73     if(maze[x][y]=='E') 
 74     {    
 75         cout<<rpath<<" ";
 76         return -1;
 77     }
 78     //右转
 79     if(maze[x+incre[ind][4]][y+incre[ind][5]]!='#'&&trace[x+incre[ind][4]][y+incre[ind][5]]==0)
 80     {
 81         rpath++;
 82         nind=(ind+1)%4;
 83         if(RDFS(x+incre[ind][4],y+incre[ind][5],nind)==-1) return -1;
 84     }
 85     if(maze[x+incre[ind][2]][y+incre[ind][3]]!='#'&&trace[x+incre[ind][2]][y+incre[ind][3]]==0)
 86     {
 87         rpath++;
 88     
 89         if(RDFS(x+incre[ind][2],y+incre[ind][3],ind)==-1) return -1;
 90     }
 91     if(maze[x+incre[ind][0]][y+incre[ind][1]]!='#'&&trace[x+incre[ind][0]][y+incre[ind][1]]==0)
 92     {
 93         rpath++;
 94         nind=(ind+3)%4;
 95         if(RDFS(x+incre[ind][0],y+incre[ind][1],nind)==-1) return -1;
 96     }
 97     if(maze[x+incre[ind][6]][y+incre[ind][7]]!='#'&&trace[x+incre[ind][6]][y+incre[ind][7]]==0)
 98     {
 99         rpath++;
100         nind=(ind+2)%4;
101         if(RDFS(x+incre[ind][6],y+incre[ind][7],nind)==-1) return -1;
102     }
103     return rpath;
104 }
105 
106 void BFS(vertex v,int ind)
107 {
108     vertex a,b;
109     bfq.push(v);
110     trace[v.x][v.y]=1;
111     while(bfq.size()!=0)
112     {
113         a=bfq.front();
114         bfq.pop();
115         if(maze[a.x+incre[ind][4]][a.y+incre[ind][5]]!='#'&&trace[a.x+incre[ind][4]][a.y+incre[ind][5]]==0)
116         {
117             trace[a.x+incre[ind][4]][a.y+incre[ind][5]]=1;
118             b.x=a.x+incre[ind][4];   b.y=a.y+incre[ind][5];   b.path=a.path+1;
119             if(maze[b.x][b.y]=='E')
120             {
121                 cout<<b.path<<endl;
122                 break;
123             }
124             bfq.push(b);
125         }
126         if(maze[a.x+incre[ind][2]][a.y+incre[ind][3]]!='#'&&trace[a.x+incre[ind][2]][a.y+incre[ind][3]]==0)
127         {
128             trace[a.x+incre[ind][2]][a.y+incre[ind][3]]=1;
129             b.x=a.x+incre[ind][2];   b.y=a.y+incre[ind][3];   b.path=a.path+1;
130             if(maze[b.x][b.y]=='E')
131             {
132                 cout<<b.path<<endl;
133                 break;
134             }            
135             bfq.push(b);            
136         }
137         if(maze[a.x+incre[ind][0]][a.y+incre[ind][1]]!='#'&&trace[a.x+incre[ind][0]][a.y+incre[ind][1]]==0)
138         {
139             trace[a.x+incre[ind][0]][a.y+incre[ind][1]]=1;
140             b.x=a.x+incre[ind][0];   b.y=a.y+incre[ind][1];   b.path=a.path+1;
141             if(maze[b.x][b.y]=='E')
142             {
143                 cout<<b.path<<endl;
144                 break;
145             }
146             bfq.push(b);        
147         }
148         if(maze[a.x+incre[ind][6]][a.y+incre[ind][7]]!='#'&&trace[a.x+incre[ind][6]][a.y+incre[ind][7]]==0)
149         {
150             trace[a.x+incre[ind][6]][a.y+incre[ind][7]]=1;
151             b.x=a.x+incre[ind][6];   b.y=a.y+incre[ind][7];   b.path=a.path+1;
152             if(maze[b.x][b.y]=='E')
153             {
154                 cout<<b.path<<endl;
155                 break;
156             }
157             bfq.push(b);        
158         }
159     }
160 }
161         
162 
163     
164     
165 
166 
167 int main()
168 {
169     int instan,w,h,i,j,sx,sy,ind;
170     char in;
171     cin>>instan;
172     for(int Num=0;Num<instan;Num++)
173     {
174         cin>>w>>h;
175         for(i=0;i<h;i++)
176             for(j=0;j<w;j++)
177             {
178                 cin>>in;
179                 maze[i][j]=in;
180                 if(maze[i][j]=='S')
181                 {
182                     sx=i;sy=j;
183                 }
184             }
185         if(sy==0) ind=0;
186         if(sx==0) ind=1;
187         if(sy==(w-1)) ind=2;
188         if(sx==(h-1)) ind=3;
189         lpath=1;
190         memset(trace,0,sizeof(trace));
191         lpath=LDFS(sx,sy,ind);
192         rpath=1,spath=1;
193         memset(trace,0,sizeof(trace));
194         rpath=RDFS(sx,sy,ind);
195         //cout<<lpath<<" "<<rpath<<endl;
196         vertex vs;
197         vs.x=sx;vs.y=sy;vs.path=1;
198         memset(trace,0,sizeof(trace));
199         BFS(vs,ind);
200         while(bfq.empty()!=1)
201         {
202             bfq.pop();
203         }
204     }
205     return 0;
206 }