POJ 1324

  1 //Result:wizmann    1324    Accepted    3112K    3454MS    G++    3200B

  2 //What's Wrong:

  3 //    1.位压缩的效率，减少无关位

  4 //    2.蛇的走动方向没有经过检测

  5 //    3.没有自己出数据检验

  6 //    4.对于某些数据相当然了

  7 #include <cstdio>

  8 #include <cstdlib>

  9 #include <cstring>

 10 #include <algorithm>

 11 #include <iostream>

 12 #include <queue>

 13 #include <bitset>

 14 

 15 using namespace std;

 16 

 17 #define SIZE 21

 18 #define INF 1<<25

 19 #define STATUS 1<<14

 20 #define print(x) cout<<x<<endl

 21 

 22 const int mx[]={0,1,0,-1};

 23 const int my[]={-1,0,1,0};

 24 int n,m,l;

 25 

 26 struct point

 27 {

 28     int x,y;

 29     point(){}

 30     point(int i_x,int i_y)

 31     {

 32         x=i_x;y=i_y;

 33     }

 34 };

 35 

 36 struct snake

 37 {

 38     point head;

 39     int status;

 40     int step;

 41 

 42     snake()

 43     {

 44         status=0;

 45         step=0;

 46     }

 47     

 48     void makeStatus(point *body)

 49     {

 50         status=0;

 51         int ptr=0;

 52         for(int i=1;i<l;i++)

 53         {

 54             int now=i;

 55             int pre=i-1;

 56             int dir=-1;

 57             for(int i=0;i<4;i++)

 58             {

 59                 if(body[pre].x-body[now].x==mx[i] &&

 60                     body[pre].y-body[now].y==my[i])

 61                 {

 62                     dir=i;

 63                     break;

 64                 }

 65             }

 66             //print("DIR:"<<dir);

 67             status |= (dir<<ptr);

 68             //print(status);

 69             ptr+=2;

 70         }

 71     }

 72 };

 73 

 74 point stone[SIZE*SIZE];

 75 queue<snake> q;

 76 bitset<STATUS> visit[SIZE][SIZE];

 77 //char visit[SIZE][SIZE][STATUS];

 78 int stone_num;

 79 

 80 inline bool inMap(int x,int y)

 81 {

 82     if(x>0 && x<=m && y>0 && y<=n) return true;

 83     else return false;

 84 }

 85 

 86 int moveSnake(int x,int y,snake& py)

 87 {

 88     for(int i=0;i<stone_num;i++)

 89     {

 90         if(x==stone[i].x && y==stone[i].y) return -1;

 91     }

 92     int status=0;

 93     point now=py.head;

 94     point head=point(x,y);

 95     int ptr=0;

 96     for(int i=0;i<l;i++)

 97     {

 98         int dir;

 99         if(now.x==x && now.y==y) return -1;

100         else

101         {

102             //print(now.x<<' '<<now.y);

103             for(int j=0;j<4;j++)

104             {

105                 if(head.x-now.x==mx[j] && head.y-now.y==my[j])

106                 {

107                     dir=j;

108                     break;

109                 }

110             }

111             if(i<l-1)

112             {

113                 status |= (dir<<ptr);

114                 dir=( (3<<ptr) & py.status )>>ptr;

115                 //print("DIR:"<<dir);

116                 ptr+=2;

117                 head=now;

118                 now.x-=mx[dir];

119                 now.y-=my[dir];

120             }

121         }

122     }

123     py.head=point(x,y);

124     py.status=status;

125     py.step++;

126     //puts("");

127     return py.status;

128 }

129 

130 int bfs()

131 {

132     int ans=INF;

133     while(!q.empty())

134     {

135         snake now=q.front();

136         q.pop();

137         int now_x=now.head.x;

138         int now_y=now.head.y;

139         //print(now_x<<' '<<now_y);

140         if(now.step>=ans || visit[now_y][now_x][now.status]) continue;

141         if(now_x==1 && now_y==1)

142         {

143             ans=now.step;

144             continue;

145         }

146         visit[now_y][now_x][now.status]=1;

147         

148         point head=now.head;

149 

150         for(int i=0;i<4;i++)

151         {

152             int nx=head.x+mx[i];

153             int ny=head.y+my[i];

154             if(!inMap(nx,ny)) continue;

155             snake npy=now;

156             int nstatus=moveSnake(nx,ny,npy);

157             //print(nstatus);

158             if(nstatus==-1) continue;

159             else q.push(npy);

160         }

161     }

162     return ans;

163 }

164 

165 

166 int main()

167 {

168     int cas=1;

169     point body[10];

170     while(scanf("%d%d%d",&n,&m,&l)!=EOF && n+m+l)

171     {

172         snake py;

173         int a,b;

174         for(int i=0;i<SIZE;i++)

175         {

176             for(int j=0;j<SIZE;j++)

177             {

178                 visit[i][j].reset();

179             }

180         }

181         while(!q.empty()) q.pop();

182         

183         for(int i=0;i<l;i++)

184         {

185             scanf("%d%d",&a,&b);

186             body[i]=point(b,a);

187         }

188         py.head=body[0];

189         py.makeStatus(body);

190         py.step=0;

191         q.push(py);

192         

193         scanf("%d",&stone_num);

194         for(int i=0;i<stone_num;i++)

195         {

196             scanf("%d%d",&a,&b);

197             stone[i]=point(b,a);

198         }

199         int ans=bfs();

200         if(ans>=INF) ans=-1;

201         

202         printf("Case %d: %d\n",cas++,ans);

203     }

204     return 0;

205 }