POJ 3083 Children of the Candy Corn（bfs求最短路／迷宫）

POJ 3083 Children of the Candy Corn（bfs求最短路／迷宫）

题目链接：http://acm.pku.edu.cn/JudgeOnline/problem?id=3083

题目描述：求最短路，求沿特定方向走迷宫的步数

所用算法：最短路用bfs求，特定方向走迷宫直接用while计数（这里写的比较繁琐，要细心，本来看题目分类是在dfs里面的，以为这要用dfs，细想想不用，而求迷宫最短路径，bfs应该是首选了）

提交情况：1次wa(忘了加<stdio.h>头文件)，一次re（在队列数组开的太小）

心得体会：好久没有做迷宫题了，今天做了一道，各种别扭。题目不难，仔细读题就可以了。求最短路实际上就是个模板，和2251一样。中间写完还出现段错误的情况，是用gets/fgets（）读map造成的，然后我就改成了逐行读字符串。题目数据并不大，因为暴搜也0ms就过了，但很纳闷为什么这个数据规模队列开成1000就re，其实也差不多了，40＊40无非就1600种情况而已，下次开数组时不能想当然，一定要走脑子后再开。

1 #include<iostream> 2 #include<stdio.h> 3 using namespace std; 4 5 #define EAST 1 6 #define WEST 2 7 #define SOUTH 3 8 #define NORTH 4 9 10 char map[100][100]; 11 struct pos 12 { 13 int x; 14 int y; 15 int pre; 16 }; 17 18 int w; 19 int h; 20 21 pos queue[20000]; 22 23 const int d1[]={1,-1,0,0}; 24 const int d2[]={0,0,1,-1}; 25 int bfs(int x,int y) 26 { 27 int head=0; 28 int tail=0; 29 queue[tail].x=x; 30 queue[tail].y=y; 31 queue[tail].pre=-1; 32 tail++; 33 pos temp; 34 pos next; 35 int step=0; 36 while(head!=tail) 37 { 38 temp.x=queue[head].x; 39 temp.y=queue[head].y; 40 head++; 41 for(int i=0;i<4;i++) 42 { 43 next.x=temp.x+d1[i]; 44 next.y=temp.y+d2[i]; 45 next.pre=head-1; 46 47 if(next.x>=0&&next.x<h&&next.y>=0&&next.y<w&&map[next.x][next.y]=='E') 48 { 49 goto END; 50 } 51 52 if(next.x>=0&&next.x<h&&next.y>=0&&next.y<w&&map[next.x][next.y]!='#') 53 { 54 queue[tail].x=next.x; 55 queue[tail].y=next.y; 56 queue[tail].pre=next.pre; 57 tail++; 58 map[next.x][next.y]='#'; 59 } 60 } 61 } 62 return -1; 63 END: 64 while(next.pre!=-1) 65 { 66 next.pre=queue[next.pre].pre; 67 step++; 68 } 69 return step; 70 } 71 72 int mleft(int x,int y,int direct) 73 { 74 int l=0; 75 while(map[x][y]!='E') 76 { 77 switch(direct) 78 { 79 case EAST: 80 if(x-1>=0&&map[x-1][y]!='#') 81 { 82 x=x-1; 83 direct=NORTH; 84 } 85 else if(y+1<w&&map[x][y+1]!='#') 86 { 87 y=y+1; 88 direct=EAST; 89 } 90 else if(x+1<h&&map[x+1][y]!='#') 91 { 92 x=x+1; 93 direct=SOUTH; 94 } 95 else if(y-1>=0&&map[x][y-1]!='#') 96 { 97 y=y-1; 98 direct=WEST; 99 } 100 l++; 101 break; 102 case SOUTH: 103 if(y+1<w&&map[x][y+1]!='#') 104 { 105 y=y+1; 106 direct=EAST; 107 } 108 else if(x+1<h&&map[x+1][y]!='#') 109 { 110 x=x+1; 111 direct=SOUTH; 112 } 113 else if(y-1>=0&&map[x][y-1]!='#') 114 { 115 y=y-1; 116 direct=WEST; 117 } 118 else if(x-1>=0&&map[x-1][y]!='#') 119 { 120 x=x-1; 121 direct=NORTH; 122 } 123 l++; 124 break; 125 126 case WEST: 127 if(x+1<h&&map[x+1][y]!='#') 128 { 129 x=x+1; 130 direct=SOUTH; 131 } 132 else if(y-1>=0&&map[x][y-1]!='#') 133 { 134 y=y-1; 135 direct=WEST; 136 } 137 else if(x-1>=0&&map[x-1][y]!='#') 138 { 139 x=x-1; 140 direct=NORTH; 141 } 142 else if(y+1<w&&map[x][y+1]!='#') 143 { 144 y=y+1; 145 direct=EAST; 146 } 147 l++; 148 break; 149 case NORTH: 150 if(y-1>=0&&map[x][y-1]!='#') 151 { 152 y=y-1; 153 direct=WEST; 154 } 155 else if(x-1>=0&&map[x-1][y]!='#') 156 { 157 x=x-1; 158 direct=NORTH; 159 } 160 else if(y+1<w&&map[x][y+1]!='#') 161 { 162 y=y+1; 163 direct=EAST; 164 } 165 else if(x+1<h&&map[x+1][y]!='#') 166 { 167 x=x+1; 168 direct=SOUTH; 169 } 170 l++; 171 break; 172 } 173 } 174 return l; 175 } 176 177 178 int mright(int x,int y,int direct) 179 { 180 int r=0; 181 while(map[x][y]!='E') 182 { 183 switch(direct) 184 { 185 case EAST: 186 if(x+1<h&&map[x+1][y]!='#') 187 { 188 x=x+1; 189 direct=SOUTH; 190 } 191 else if(y+1<w&&map[x][y+1]!='#') 192 { 193 y=y+1; 194 direct=EAST; 195 } 196 else if(x-1>=0&&map[x-1][y]!='#') 197 { 198 x=x-1; 199 direct=NORTH; 200 } 201 else if(y-1>=0&&map[x][y-1]!='#') 202 { 203 y=y-1; 204 direct=WEST; 205 } 206 r++; 207 break; 208 case NORTH: 209 if(y+1<w&&map[x][y+1]!='#') 210 { 211 y=y+1; 212 direct=EAST; 213 } 214 else if(x-1>=0&&map[x-1][y]!='#') 215 { 216 x=x-1; 217 direct=NORTH; 218 } 219 else if(y-1>=0&&map[x][y-1]!='#') 220 { 221 y=y-1; 222 direct=WEST; 223 } 224 else if(x+1<h&&map[x+1][y]!='#') 225 { 226 x=x+1; 227 direct=SOUTH; 228 } 229 r++; 230 break; 231 case WEST: 232 if(x-1>=0&&map[x-1][y]!='#') 233 { 234 x=x-1; 235 direct=NORTH; 236 } 237 else if(y-1>=0&&map[x][y-1]!='#') 238 { 239 y=y-1; 240 direct=WEST; 241 } 242 else if(x+1<h&&map[x+1][y]!='#') 243 { 244 x=x+1; 245 direct=SOUTH; 246 } 247 else if(y+1<w&&map[x][y+1]!='#') 248 { 249 y=y+1; 250 direct=EAST; 251 } 252 r++; 253 break; 254 case SOUTH: 255 if(y-1>=0&&map[x][y-1]!='#') 256 { 257 y=y-1; 258 direct=WEST; 259 } 260 else if(x+1<h&&map[x+1][y]!='#') 261 { 262 x=x+1; 263 direct=SOUTH; 264 } 265 else if(y+1<w&&map[x][y+1]!='#') 266 { 267 y=y+1; 268 direct=EAST; 269 } 270 else if(x-1>=0&&map[x-1][y]!='#') 271 { 272 x=x-1; 273 direct=NORTH; 274 } 275 r++; 276 break; 277 } 278 } 279 return r; 280 } 281 282 283 int main() 284 { 285 //freopen("data.in","r",stdin); 286 int testcase; 287 cin>>testcase; 288 while(testcase--) 289 { 290 int lv; 291 int rv; 292 int mv; 293 cin>>w>>h; 294 string str; 295 int x,y,direct; 296 for(int i=0;i<h;i++) 297 { 298 cin>>str; 299 const char *p=str.c_str(); 300 for(int j=0;j<w;j++) 301 { 302 map[i][j]=p[j]; 303 } 304 } 305 for(int i=0;i<h;i++) 306 { 307 for(int j=0;j<w;j++) 308 { 309 if(map[i][j]=='S') 310 { 311 x=i; 312 y=j; 313 map[i][j]='#'; 314 } 315 } 316 } 317 318 if(x==0) 319 direct=SOUTH; 320 else if(x==h-1) 321 direct=NORTH; 322 else if(y==0) 323 direct=EAST; 324 else if(y==w-1) 325 direct=WEST; 326 327 lv=mleft(x,y,direct)+1; 328 rv=mright(x,y,direct)+1; 329 mv=bfs(x,y)+1; 330 printf("%d %d %d\\n",lv,rv,mv); 331 } 332 }