UVa 11624 大火蔓延的迷宫

  1 #include<iostream> 
  2 #include<algorithm>
  3 #include<queue>
  4 #include<cstring>
  5 using namespace std;
  6 
  7 const int maxn = 1000 + 5;
  8 
  9 int map[maxn][maxn];
 10 int fire[maxn][maxn];
 11 int vis[maxn][maxn];
 12 
 13 int dx, dy;
 14 int n, m;
 15 
 16 int sx[] = { 0, 0, 1, -1 };
 17 int sy[] = { 1, -1, 0, 0 };
 18 
 19 
 20 struct node
 21 {
 22     int x, y;
 23     int t;
 24 };
 25 
 26 void bfs1()
 27 {
 28     memset(fire, -1, sizeof(fire));
 29     queue<node> Q;
 30     for (int i = 0; i < n;i++)
 31     for (int j = 0; j < m; j++)
 32     {
 33         if (map[i][j] == -1)
 34         {
 35             node p;
 36             p.x = i;
 37             p.y = j;
 38             p.t = 1;
 39             Q.push(p);
 40             fire[i][j] = 1;
 41         }
 42     }
 43     while (!Q.empty())
 44     {
 45         node p = Q.front();
 46         Q.pop();
 47         for (int k = 0; k < 4; k++)
 48         {
 49             int x = p.x + sx[k];
 50             int y = p.y + sy[k];
 51             if (x < 0 || x >= n || y < 0 || y >= m)  continue;
 52             if (map[x][y] != 1)     continue;
 53             if (fire[x][y] != -1)   continue;
 54             fire[x][y] = p.t + 1;
 55             node u;
 56             u.x = x;
 57             u.y = y;
 58             u.t = p.t + 1;
 59             Q.push(u);
 60         }
 61     }
 62 }
 63 
 64 
 65 int bfs2()
 66 {
 67     memset(vis, 0, sizeof(vis));
 68     queue<node> Q;
 69     node p;
 70     p.x = dx;
 71     p.y = dy;
 72     p.t = 1;
 73     Q.push(p);
 74     vis[dx][dy] = 1;
 75     while (!Q.empty())
 76     {
 77         node p = Q.front();
 78         Q.pop();
 79         if (p.x == 0 || p.x == n - 1 || p.y == 0 || p.y == m - 1)  return p.t;
 80         for (int k = 0; k < 4; k++)
 81         {
 82             int x = p.x + sx[k];
 83             int y = p.y + sy[k];
 84             if (vis[x][y])   continue;
 85             if (x < 0 || x >= n || y < 0 || y >= m)  continue;
 86             if (map[x][y] != 1)   continue;
 87             if (fire[x][y]!=-1 && p.t + 1 >= fire[x][y])   continue;
 88             node u;
 89             u.x = x;
 90             u.y = y;
 91             u.t = p.t + 1;
 92             Q.push(u);
 93             vis[x][y] = 1;
 94         }
 95     }
 96     return -1;
 97 }
 98 
 99 
100 int main()
101 {
102     ios::sync_with_stdio(false);
103     //freopen("D:\\txt.txt", "r", stdin);
104     int T;
105     char c;
106     cin >> T;
107     while (T--)
108     {
109         cin >> n >> m;
110         for (int i = 0; i < n;i++)
111         for (int j = 0; j < m; j++)
112         {
113             cin >> c;
114             if (c == ‘#‘)  map[i][j] = 0;
115             else if (c == ‘F‘)  map[i][j] = -1;
116             else if (c == ‘J‘)
117             {
118                 map[i][j] = 1;
119                 dx = i; 
120                 dy = j;
121             }
122             else map[i][j] = 1;
123         }
124 
125         bfs1();
126         int ans=bfs2();
127         if (ans == -1)  cout << "IMPOSSIBLE" << endl;
128         else cout << ans << endl;
129     }
130 }