【HDOJ】1885 Key Task

状态压缩+BFS，一次AC。

 /* 1885 */
 #include <iostream>
 #include <queue>
 #include <cstring>
 #include <cstdio>
 #include <cstdlib>
 using namespace std;

 #define MAXN 105

 bool visit[MAXN][MAXN][];

 typedef struct node_t {
     int x, y, t, k;
     node_t() {}
     node_t(int xx, int yy, int tt, int kk) {
         x = xx; y = yy; t = tt; k = kk;
     }
 } node_t;

 int n, m;
 node_t beg;
 char map[MAXN][MAXN];
 int dir[][] = {
     -,,,,,-,,
 };

 inline bool check(int x, int y) {
     return x< || x>=n || y< || y>=m;
 }

 int bfs() {
     int i, j, k;
     int x, y, t;
     node_t nd;
     queue<node_t> Q;

     memset(visit, false, sizeof(visit));
     visit[beg.x][beg.y][beg.k] = true;
     Q.push(beg);

     while (!Q.empty()) {
         nd = Q.front();
         Q.pop();
         t = nd.t + ;
         for (i=; i<; ++i) {
             x = nd.x + dir[i][];
             y = nd.y + dir[i][];
             if (check(x, y) || map[x][y]=='#')
                 continue;
             if (map[x][y] == 'X')
                 return t;
             k = nd.k;
             if (map[x][y]>='A' && map[x][y]<='D') {
                 j = map[x][y] - 'A';
                 if ((nd.k & (<<j)) == )
                     continue;
             } else if (map[x][y]>='a' && map[x][y]<='d') {
                 j = map[x][y] - 'a';
                 k |= (<<j);
             }
             if (visit[x][y][k])
                 continue;
             visit[x][y][k] = true;
             Q.push(node_t(x, y, t, k));
         }
     }

     return -;
 }

 int main() {
     int i, j, k;

     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     beg.k = beg.t = ;
     while (scanf("%d%d",&n,&m)!=EOF && (n||m)) {
         for (i=; i<n; ++i) {
             scanf("%s", map[i]);
             for (j=; j<m; ++j) {
                 if (map[i][j] == '*') {
                     beg.x = i;
                     beg.y = j;
                 } else if (map[i][j] == 'Y') {
                     map[i][j] = 'A';
                 } else if (map[i][j] == 'R') {
                     map[i][j] = 'C';
                 } else if (map[i][j] == 'G') {
                     map[i][j] = 'D';
                 } else if (map[i][j] == 'y') {
                     map[i][j] = 'a';
                 } else if (map[i][j] == 'r') {
                     map[i][j] = 'c';
                 } else if (map[i][j] == 'g') {
                     map[i][j] = 'd';
                 }
             }
         }
         k = bfs();
         if (k < )
             puts("The poor student is trapped!");
         else
             printf("Escape possible in %d steps.\n", k);
     }

     return ;
 }