P1608 路径统计

\(dijkstra\)最短路径计数，注意判输入时的重复数据(=_=)

const int N=2010;
struct Node
{
    int a,b,c;
    bool operator<(const Node &W) const
    {
        if(a == W.a)
        {
            if(b == W.b)
                return c<W.c;
            else return b<W.b;
        }
        else return a<W.a;
    }
};
set<Node> S;
vector<PII> g[N];
int dist[N];
bool vis[N];
int f[N];
int n,m;

void dijkstra()
{
    memset(dist,0x3f,sizeof dist);
    priority_queue<PII,vector<PII>,greater<PII> > heap;
    dist[1]=0;
    heap.push({0,1});
    f[1]=1;

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

        if(vis[t]) continue;
        vis[t]=true;

        for(int i=0;i<g[t].size();i++)
        {
            int j=g[t][i].fi,w=g[t][i].se;
            if(dist[j] > dist[t]+w)
            {
                dist[j]=dist[t]+w;
                f[j]=f[t];
                heap.push({dist[j],j});
            }
            else if(dist[j] == dist[t]+w)
            {
                f[j]+=f[t];
            }
        }
    }
}

int main()
{
    ios;
    cin>>n>>m;

    while(m--)
    {
        int a,b,c;
        cin>>a>>b>>c;
        if(S.count({a,b,c})) continue;
        S.insert({a,b,c});
        g[a].pb({b,c});
    }

    dijkstra();

    if(dist[n] == INF) cout<<"No answer"<<endl;
    else cout<<dist[n]<<' '<<f[n]<<endl;

    //system("pause");
}