Submission #758097

#	Time	Username	Problem	Language	Result	Execution time	Memory
758097		jasmin	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	23 ms	5288 KiB

ho_t4

#include<bits/stdc++.h>
using namespace std;
#define int long long

const int INF=1e17;

struct graph{
    vector<vector<pair<int,int> > >adi;
    vector<int> c;
    vector<int> d;

    graph(int n, int m){
        adi.assign(n, {});
        c.assign(m, 0);
        d.assign(m, 0);
    }

};

void dijkstra(int start, vector<int>& dist, int n, graph& g){

    dist.assign(n, INF);
    vector<bool> vis(n, false);
    priority_queue<pair<int,int> > pq;

    dist[start]=0;
    pq.push({-0, start});

    while(!pq.empty()){
        int v=pq.top().second;
        pq.pop();

        if(vis[v]){
            continue;
        }
        vis[v]=true;

        for(auto [u, ind]: g.adi[v]){

            if(dist[v]+g.c[ind] < dist[u]){
                dist[u] = dist[v] + g.c[ind];
                pq.push({-dist[u], u});
            }

        }
    }

}

vector<int> find_sp(int a, int b, vector<int>& froma, vector<int>& tob, graph& g){
    vector<int> p;
    int dist=froma[b];

    if(dist==INF) return {};
    
    int v=a;
    while(v!=b){

        for(auto [u, ind]: g.adi[v]){

            if(froma[v] + g.c[ind] + tob[u] == dist){
                p.push_back(ind);
                v=u;
                break;
            }

        }

    }

    return p;
}

signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    int n, m;
    cin >> n >> m;
    graph g(n, m);
    graph rev(n, m);
    vector<pair<int,int> > edge(m);
    for(int i=0; i<m; i++){
        int a, b;
        cin >> a >> b >> g.c[i] >> g.d[i];
        a--; b--;
        g.adi[a].push_back({b, i});

        rev.c[i]=g.c[i];
        rev.d[i]=g.d[i];
        rev.adi[b].push_back({a, i});

        edge[i]={a, b};
    }

    //distances
    vector<int> from0(n, INF);
    dijkstra(0, from0, n, g);
    vector<int> to0(n, INF);
    dijkstra(0, to0, n, rev);

    vector<int> fromn(n, INF);
    dijkstra(n-1, fromn, n, g);
    vector<int> ton(n, INF);
    dijkstra(n-1, ton, n, rev);

    cout << "blub\n" << flush;
    return 0;

    //paths
    vector<int> path1=find_sp(0, n-1, from0, ton, g);
    vector<int> path2=find_sp(n-1, 0, fromn, to0, g);
    
    vector<bool> used(m, false);
    for(auto e: path1){
        used[e]=true;
    }
    for(auto e: path2){
        used[e]=true;
    }


    //possibility 0: turning no edge
    int ans=INF;
    ans = min(ans, from0[n-1] + fromn[0]);

    //possibility 1: edge not on path
    for(int i=0; i<m; i++){
        if(used[i]) continue;

        auto [a, b]=edge[i];

        int d1=from0[b] + g.c[i] + ton[a] + fromn[0];
        int d2=from0[n-1] + fromn[b] + g.c[i] + to0[a];

        int d=min(d1, d2) + g.d[i];
        ans=min(ans, d);
    }

    //possibility 2: edge on path
    vector<int> path=path1;
    for(auto e: path2) path.push_back(e);

    for(auto e: path){

        graph neu(n, m);
        for(int i=0; i<m; i++){
            neu.c[i]=g.c[i];
            neu.d[i]=g.d[i];

            auto [a, b]=edge[i];
            if(i==e){
                neu.adi[b].push_back({a, i});
            }
            else{
                neu.adi[a].push_back({b, i});
            }
        }

        int d=0;
        vector<int> dist(n, INF);
        dijkstra(0, dist, n, neu);
        d=dist[n-1];

        dijkstra(n-1, dist, n, neu);
        d+=dist[0];

        ans=min(ans, d);
    }

    //output
    if(ans==INF){
        cout << -1 << "\n";
    }
    else{
        cout << ans << "\n";
    }
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63