hdu 1242 ( Rescue )

Problem : 1242 ( Rescue )     Judge Status : Accepted
思路：优先队列+BFS 
#include<iostream>
#include<queue>
#include<string>
using namespace std;
int n,m,ans;
string a[200];
int vis[200][200],ok;
int dir[4][2]={-1,0,0,1,1,0,0,-1};
struct node
{
    int x,y,dis;
    node(int _x=0,int _y=0,int _dis=0):x(_x),y(_y),dis(_dis){};
    friend bool operator<(const node &a,const node & b)
    {
        return a.dis>b.dis;
    }
};
node s,e;
void BFS()
{
    ok=0;
    priority_queue <node> q;
    s.dis=0;
    q.push(s);
    vis[s.x][s.y]=1;
    while(!q.empty())
    {
        node t=q.top();
        q.pop();
        for(int k=0;k<4;k++)
        {
            int i=t.x+dir[k][0];
            int j=t.y+dir[k][1];
            if(i>=0&&i<n&&j>=0&&j<m&&!vis[i][j]&&a[i][j]!='#')
            {
                vis[i][j]=1;
                if(a[i][j]=='x')
                {
                    q.push(node(i,j,t.dis+2));
                }
                else if(a[i][j]=='.')
                {
                    q.push(node(i,j,t.dis+1));
                }
                else if(a[i][j]=='a')
                {
                    
                    ans=t.dis+1;
                    ok=1;
                    return;
                }
            }
        }
    }
}
int main()
{
    
    while(cin>>n>>m)
    {
        memset(vis,0,sizeof(vis));
        for(int i=0;i<n;i++)
        {
            cin>>a[i];
            for(int j=0;j<m;j++)
            {
                if(a[i][j]=='a'){e.x=i;e.y=j;}
                if(a[i][j]=='r'){s.x=i,s.y=j;}
            }
        }
        BFS();
        if(ok)cout<<ans<<endl;
        else cout<<"Poor ANGEL has to stay in the prison all his life."<<endl;
    }
}