BZOJ1054(搜索)

大力搜，状态用一个16位的数字表示。

 #include <bits/stdc++.h>

 using namespace std;

 #define rep(i,a,b)              for(int i(a); i <= (b); ++i)

 const int A     =              +       ;

 struct node{int x, y; } op[A];
 struct Node{int num, step;} now, np;

 char st[A][A];
 int f[A][A];
 int h[ << ];
 int x, y, nx, ny, s, t, cnt = ;

 queue <Node> Q;

 int main(){

     rep(i, , ) scanf("%s", st[i] + );
     cnt = ;
     rep(i, , ) rep(j, , ) f[i][j] = cnt++;
     rep(i, , ) rep(j, , ) f[i][j] = f[i - ][j];

     s = , t = ;

     rep(i, , ) rep(j, , ) if (st[i][j] == '') s |= ( << f[i][j]);
     rep(i, , ) rep(j, , ) if (st[i][j] == '') t |= ( << f[i][j]);

     cnt = ;

     rep(i, , ) rep(j, , ){ op[++cnt].x = f[i][j], op[cnt].y = f[i + ][j];}
     rep(i, , ) rep(j, , ){ op[++cnt].x = f[i][j], op[cnt].y = f[i][j + ];}

     memset(h, , sizeof h); h[s] = ; Q.push({s, });

     while (!Q.empty()){
         np = Q.front(); Q.pop();
         if (np.num == t){
             printf("%d\n", np.step);
             break;
         }
         rep(i, , cnt){
             now = np;
             x = op[i].x, y = op[i].y;
             nx = (now.num >> x) & , ny = (now.num >> y) & ;
             if (nx ^ ny){
                 now.num ^= ( << x);
                 now.num ^= ( << y);
             }

             if (!h[now.num]){
                 h[now.num] = ;
                 Q.push({now.num, now.step + });
             }
         }
     }

     return ;

 }