Rescue BFS+优先队列 杭电1242

思路 ： 优先队列  每次都取最小的时间，遇到了终点直接就输出

#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
const int N=;

int n,m,sa,ea,sr,er;

char arr[N][N];
int bb[N][N]={};

struct stu{
    int a,b;
    int time;
    bool friend operator <(const stu &a,const stu &b){
        return a.time>b.time;
    }
};

int a[]={,,,-};
int br[]={,,-,};

void bfs(){
    priority_queue<stu>que;
    stu s;
    s.a=sa;
    s.b=ea;
    s.time=;
    que.push(s);
    bb[sa][ea]=;
    int flag=;
    while(que.size()){
        stu p;
        p=que.top();
        que.pop();
        stu st;
        for(int i=;i<;i++){
            st.a=p.a+a[i];
            st.b=p.b+br[i];
            if(st.a>=&&st.b>=&&st.a<n&&st.b<m&&bb[st.a][st.b]!=&&arr[st.a][st.b]!='#'){
                bb[st.a][st.b]=;
                if(arr[st.a][st.b]=='x')
                    st.time=p.time+;
                else {
                    st.time=p.time+;
                }
                que.push(st);
                if(st.a==sr&&st.b==er)
                    {
                        cout<<st.time<<endl;
                        return ;
                    }
            }
        }
    }
    cout<<"Poor ANGEL has to stay in the prison all his life."<<endl;
    return ;
}

int main()
{
    while(cin>>n>>m){
        memset(bb,,sizeof(bb));
        for(int i=;i<n;i++)
            scanf("%s",&arr[i]);
        for(int i=;i<n;i++){
            for(int j=;j<m;j++)
            {
                if(arr[i][j]=='a'){
                    sa=i;
                    ea=j;
                }
                else if(arr[i][j]=='r'){
                    sr=i;
                    er=j;
                }
            }
        }
        bfs();
    }

    return ;
}