hdu 1242 Rescue (BFS)

Rescue

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 12927    Accepted Submission(s): 4733

Problem Description

Angel was caught by the MOLIGPY! He was put in prison by Moligpy. The prison is described as a N * M (N, M <= 200) matrix. There are WALLs, ROADs, and GUARDs in the prison.

Angel's friends want to save Angel. Their task is: approach Angel. We assume that "approach Angel" is to get to the position where Angel stays. When there's a guard in the grid, we must kill him (or her?) to move into the grid. We assume that we moving up, down, right, left takes us 1 unit time, and killing a guard takes 1 unit time, too. And we are strong enough to kill all the guards.

You have to calculate the minimal time to approach Angel. (We can move only UP, DOWN, LEFT and RIGHT, to the neighbor grid within bound, of course.)

 

Input

First line contains two integers stand for N and M.

Then N lines follows, every line has M characters. "." stands for road, "a" stands for Angel, and "r" stands for each of Angel's friend.

Process to the end of the file.

 

Output

For each test case, your program should output a single integer, standing for the minimal time needed. If such a number does no exist, you should output a line containing "Poor ANGEL has to stay in the prison all his life." 

 

Sample Input

7 8
#.#####.
#.a#..r.
#..#x...
..#..#.#
#...##..
.#......
........

 

Sample Output

13

 

Author

CHEN, Xue

 

Source

ZOJ Monthly, October 2003

 

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 //31MS    356K    1410 B    C++
 /*

     题意：
         从点a到点r，求最短步数

     BFS：
         典型的BFS，这题数据有点怪.最好用优先队列实现bfs。 

 */
 #include<iostream>
 #include<cstdio>
 #include<queue>
 using namespace std;
 int mov[][]={,,,,-,,,-};
 char map[][];
 int bx,by,n,m;
 struct node
 {
     int x,y,step;
     friend bool operator < (node a,node b)
     {
         return a.step>b.step;
     }
 };
 void bfs(int x,int y)
 {
      priority_queue <node> Q;
      node t={x,y,};
      Q.push(t);
      while(!Q.empty())
      {
          t=Q.top();
          Q.pop();
          for(int i=;i<;i++)
          {
              node tt=t;
              tt.x+=mov[i][];
              tt.y+=mov[i][];
              tt.step++;
              if(tt.x>=&&tt.x<n&&tt.y>=&&tt.y<m&&map[tt.x][tt.y]!='#')
              {
                  if(map[tt.x][tt.y]=='r')
                  {
                      cout<<tt.step<<endl;
                      return;
                  }
                  else if(map[tt.x][tt.y]=='x')
                     tt.step++;
                  map[tt.x][tt.y]='#';
                  Q.push(tt);
              }
          }
      }
      cout<<"Poor ANGEL has to stay in the prison all his life.\n";
 }
 int main(void)
 {
     int i,j;
     while(scanf("%d%d",&n,&m)!=EOF)
     {
         for(i=;i<n;i++)
             for(j=;j<m;j++)
             {
                 cin>>map[i][j];
                 if(map[i][j]=='a')
                     bx=i,by=j;
             }
         bfs(bx,by);
     }
     return ;
 }