HDU 1242 Rescue

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...
..#..#.#
#...##..
.#......
........

本題注意朋友可能有多个，造成时间长的先到达终点。这时我们可以用优先队列。

LAGUAGE：C++

CODE：

#include<stdio.h>
#include<queue>
#include<cstring>
using namespace std;
const int dir[4][2]={{0,1},{1,0},{0,-1},{-1,0}};
char matrix[202][202];
char used[202][202];
int n,m;
int endx,endy;
struct node
{
	int x,y;
	int step;
	friend bool operator < (const node &a, const node &b)
    {
        return a.step > b.step;
    }
};
int bfs(int startx,int starty)
{
	node cur,after;
	priority_queue<node>que;
	int x,y,i;
	memset(used,0,sizeof(used));
	cur.x=startx,cur.y=starty;
	cur.step=0;
	used[startx][starty]=1;
	que.push(cur);
	while(!que.empty())
	{
		after=que.top();
		que.pop();
		if(after.x==endx&&after.y==endy)
		{
			return after.step;
		}
		for(i=0;i<4;i++)
		{
			x=after.x+dir[i][0],y=after.y+dir[i][1];
			if(x>=0&&x<n&&y>=0&&y<m&&!used[x][y]&&matrix[x][y]!='#')
			{
				cur.x=x,cur.y=y,cur.step=after.step+1;
				used[x][y]=1;
				if(matrix[x][y]=='x')
				cur.step++;
				que.push(cur);
			}
		}
	}
	return -1;
}

int main()
{
	int startx,starty,i,j,ans;
	while(scanf("%d%d",&n,&m)!=EOF)
	{
		getchar();
		for(i=0;i<n;i++)
		{
			for(j=0;j<m;j++)
			{
				scanf("%c",&matrix[i][j]);
				if(matrix[i][j]=='r')
					startx=i,starty=j;
				else if(matrix[i][j]=='a')
					endx=i,endy=j;
			}
			getchar();
		}
		ans=bfs(startx,starty);
		if(ans==-1)
		printf("Poor ANGEL has to stay in the prison all his life.\n");
		else printf("%d\n",ans);
	}
}