HDU 1242 Rescue

由于边权有\(1\)和\(2\)两种情况，所以就不能用裸的\(BFS\)了，改成优先队列\(BFS\)(其实就是\(dijkstra\))。

const int N=210;
struct Node
{
    int dis;
    int x,y;
    bool operator>(const Node &W) const
    {
        return dis>W.dis;
    }
};
char g[N][N];
int dist[N][N];
bool vis[N][N];
int n,m;
PII st,ed;

bool check(int x,int y)
{
    return x>=0 && x<n && y>=0 && y<m;
}

int bfs()
{
    memset(dist,0x3f,sizeof dist);
    memset(vis,0,sizeof vis);
    priority_queue<Node,vector<Node>,greater<Node> > heap;
    dist[st.fi][st.se]=0;
    heap.push({0,st.fi,st.se});

    while(heap.size())
    {
        Node t=heap.top();
        heap.pop();

        if(t.x == ed.fi && t.y == ed.se) return dist[t.x][t.y];

        if(vis[t.x][t.y]) continue;
        vis[t.x][t.y]=true;

        for(int i=0;i<4;i++)
        {
            int a=t.x+dx[i],b=t.y+dy[i];
            if(!check(a,b) || g[a][b] == '#') continue;

            if(g[a][b] == 'x')
            {
                if(dist[a][b]>dist[t.x][t.y]+2)
                {
                    dist[a][b]=dist[t.x][t.y]+2;
                    heap.push({dist[a][b],a,b});
                }
            }
            else
            {
                if(dist[a][b]>dist[t.x][t.y]+1)
                {
                    dist[a][b]=dist[t.x][t.y]+1;
                    heap.push({dist[a][b],a,b});
                }
            }
        }
    }
    return -1;
}

int main()
{
    while(cin>>n>>m)
    {
        for(int i=0;i<n;i++) scanf("%s",&g[i]);

        for(int i=0;i<n;i++)
            for(int j=0;j<m;j++)
            {
                if(g[i][j] == 'r') st={i,j};
                if(g[i][j] == 'a') ed={i,j};
            }

        int t=bfs();
        if(t == -1) puts("Poor ANGEL has to stay in the prison all his life.");
        else cout<<t<<endl;
    }
    //system("pause");
}