hdu 1242 rescue （优先队列 bfs）

#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#include<iostream>
#include<algorithm>
using namespace std;
char mat[300][300];
int vis[300][300];
struct Node
{
int x,y,coun;
friend bool operator < (Node a,Node b){ return a.coun>b.coun; }  //小的先出列
};
int sx,sy,ex,ey;
int op[4][2]={1,0,-1,0,0,1,0,-1};
int n,m;
int ans;
bool fit(Node a)
{
if(0<=a.x&&a.x<n&&0<=a.y&&a.y<m&&vis[a.x][a.y]==0&&mat[a.x][a.y]!='#') return true;
return false;
}
void bfs()
{
priority_queue<Node> q;
Node f;
f.x=sx;
f.y=sy;
f.coun=0;
q.push(f);
while(!q.empty())
{
Node now=q.top();
q.pop();
vis[now.x][now.y]=1;
if(mat[now.x][now.y]=='r') {ans=now.coun;break;}
for(int i=0;i<4;i++)
{
Node next;
next.x=now.x+op[i][0];
next.y=now.y+op[i][1];
if(fit(next))
{
if(mat[next.x][next.y]=='.'||mat[next.x][next.y]=='r')
next.coun=now.coun+1;
else if(mat[next.x][next.y]=='x')
next.coun=now.coun+2;
q.push(next);
}
}
}
}
int main()
{
int i,j,k;
while(scanf("%d%d",&n,&m)!=EOF)
{
ans=-1;
memset(vis,0,sizeof(vis));
for(i=0;i<n;i++)
{
scanf("%s",mat[i]);
for(j=0;j<m;j++)
{
if(mat[i][j]=='a') {sx=i;sy=j;}
}
}
bfs();
if(ans>-1)
printf("%d\n",ans);
else printf("Poor ANGEL has to stay in the prison all his life.\n");
}
return 0;
}