HDU 1026 Ignatius and the Princess I（带路径的BFS）

http://acm.hdu.edu.cn/showproblem.php?pid=1026

题意:给出一个迷宫，求出到终点的最短时间路径。

这道题目在迷宫上有怪物，不同HP的怪物会损耗不同的时间，这个时候可以用优先队列，每次让时间最短的出队列。由于最后还需要输出路径，所以需要设置一个数组来保存路径。

 #include<iostream>
 #include<queue>
 #include<cstring>
 using namespace std;

 const int maxn =  + ;

 struct node
 {
     int x, y;
     int time;
     friend bool operator < ( node a, node b)   //重载<号
     {
         return b.time<a.time;
     }
 };

 char map[maxn][maxn];
 int visited[maxn][maxn];
 int path[maxn][maxn];
 int  n, m;
 int d[][] = { { ,  }, { -,  }, { ,  }, { , - } };

 int bfs()
 {
     node q,now;
     priority_queue<node> p;
     q.x = ;
     q.y = ;
     q.time = ;
     p.push(q);
     while (!p.empty())
     {
         q = p.top();
         p.pop();
         if (q.x == n -  && q.y == m - )  return q.time;
         for (int i = ; i < ; i++)
         {
             int xx = q.x + d[i][];
             int yy = q.y + d[i][];
             now.x = xx;
             now.y = yy;
             now.time = q.time;
             if (xx >=  && xx < n && yy >=  && yy < m && map[xx][yy]!='X' && !visited[xx][yy])
             {
                 if (map[xx][yy] == '.')   now.time++;
                 else now.time =now.time+ (map[xx][yy] - ''+);
                 visited[xx][yy] = ;
                 path[xx][yy] = i + ;     //记录路径
                 p.push(now);
             }
         }
     }
     return -;
 }

 int temp;

 void print(int x, int y)
 {
     int xx, yy;
     if (path[x][y] == )   return;
     xx = x - d[path[x][y] - ][];   //寻找第一个路径点
     yy = y - d[path[x][y] - ][];
     print(xx, yy);
     printf("%ds:(%d,%d)->(%d,%d)\n", temp++, xx, yy, x, y);
     if (map[x][y] <= '' && map[x][y] >= '')
     {
         int m = map[x][y] - '';
         while (m--)    printf("%ds:FIGHT AT (%d,%d)\n", temp++, x, y);
     }
 }

 int main()
 {
     while (cin >> n >> m && (n||m))
     {
         memset(visited, , sizeof(visited));
         memset(path, , sizeof(path));
         for (int i = ; i < n;i++)
         for (int j = ; j < m; j++)
             cin >> map[i][j];
         visited[][] = ;
         int ans=bfs();
         if (ans == -)  cout << "God please help our poor hero." << endl;
         else
         {
             cout << "It takes " << ans << " seconds to reach the target position, let me show you the way." << endl;
             temp = ;
             print(n - ,m - );
         }
         cout << "FINISH" << endl;
     }
     return ;
 }