【HDOJ】2531 Catch him

简单BFS。就是要把所有的D点当成一个整体考虑（整体移动）。

 /* 2531 */
 #include <iostream>
 #include <queue>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 using namespace std;

 #define MAXN 105

 typedef struct {
     int x[], y[];
     int t;
 } node_t;

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

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

 int bfs() {
     int i, j, k;
     node_t nd, tmp;
     queue<node_t> Q;
     bool flag, catchQ;

     memset(visit, 0x3f, sizeof(visit));
     visit[beg.x[]][beg.y[]] = beg.t;
     Q.push(beg);

     while (!Q.empty()) {
         nd = Q.front();
         Q.pop();
         tmp.t = nd.t + ;
         for (i=; i<; ++i) {
             flag = true;
             catchQ = false;
             for (j=; j<dn; ++j) {
                 tmp.x[j] = nd.x[j] + dir[i][];
                 tmp.y[j] = nd.y[j] + dir[i][];
                 if (check(tmp.x[j], tmp.y[j]) || map[tmp.x[j]][tmp.y[j]]=='O') {
                     flag = false;
                     break;
                 }
                 if (map[tmp.x[j]][tmp.y[j]] == 'Q') {
                     catchQ = true;
                 }
             }
             if (flag) {
                 if (catchQ)
                     return tmp.t;
                 if (visit[tmp.x[]][tmp.y[]] > tmp.t) {
                     visit[tmp.x[]][tmp.y[]] = tmp.t;
                     Q.push(tmp);
                 }
             }
         }
     }

     return -;
 }

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

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

     beg.t = ;
     while (scanf("%d%d",&n,&m)!=EOF && (n||m)) {
         dn = ;
         for (i=; i<n; ++i) {
             scanf("%s", map[i]);
             for (j=; j<m; ++j) {
                 if (map[i][j] == 'D') {
                     beg.x[dn] = i;
                     beg.y[dn] = j;
                     ++dn;
                 }
             }
         }
         k = bfs();
         if (k < )
             puts("Impossible");
         else
             printf("%d\n", k);
     }

     return ;
 }