简单BFS。就是要把所有的D点当成一个整体考虑（整体移动）。
1 /* 2531 */ 2 #include <iostream> 3 #include <queue> 4 #include <cstdio> 5 #include <cstring> 6 #include <cstdlib> 7 using namespace std; 8 9 #define MAXN 105 10 11 typedef struct { 12 int x[21], y[21]; 13 int t; 14 } node_t; 15 16 int dn, n, m; 17 int visit[MAXN][MAXN]; 18 char map[MAXN][MAXN]; 19 node_t beg; 20 int dir[4][2] = { 21 -1,0,1,0,0,-1,0,1 22 }; 23 24 inline bool check(int x, int y) { 25 return x<0 || x>=n || y<0 || y>=m; 26 } 27 28 int bfs() { 29 int i, j, k; 30 node_t nd, tmp; 31 queue<node_t> Q; 32 bool flag, catchQ; 33 34 memset(visit, 0x3f, sizeof(visit)); 35 visit[beg.x[0]][beg.y[0]] = beg.t; 36 Q.push(beg); 37 38 while (!Q.empty()) { 39 nd = Q.front(); 40 Q.pop(); 41 tmp.t = nd.t + 1; 42 for (i=0; i<4; ++i) { 43 flag = true; 44 catchQ = false; 45 for (j=0; j<dn; ++j) { 46 tmp.x[j] = nd.x[j] + dir[i][0]; 47 tmp.y[j] = nd.y[j] + dir[i][1]; 48 if (check(tmp.x[j], tmp.y[j]) || map[tmp.x[j]][tmp.y[j]]=='O') { 49 flag = false; 50 break; 51 } 52 if (map[tmp.x[j]][tmp.y[j]] == 'Q') { 53 catchQ = true; 54 } 55 } 56 if (flag) { 57 if (catchQ) 58 return tmp.t; 59 if (visit[tmp.x[0]][tmp.y[0]] > tmp.t) { 60 visit[tmp.x[0]][tmp.y[0]] = tmp.t; 61 Q.push(tmp); 62 } 63 } 64 } 65 } 66 67 return -1; 68 } 69 70 int main() { 71 int i, j, k; 72 73 #ifndef ONLINE_JUDGE 74 freopen("data.in", "r", stdin); 75 freopen("data.out", "w", stdout); 76 #endif 77 78 beg.t = 0; 79 while (scanf("%d%d",&n,&m)!=EOF && (n||m)) { 80 dn = 0; 81 for (i=0; i<n; ++i) { 82 scanf("%s", map[i]); 83 for (j=0; j<m; ++j) { 84 if (map[i][j] == 'D') { 85 beg.x[dn] = i; 86 beg.y[dn] = j; 87 ++dn; 88 } 89 } 90 } 91 k = bfs(); 92 if (k < 0) 93 puts("Impossible"); 94 else 95 printf("%d ", k); 96 } 97 98 return 0; 99 }