Submission #1088480

#	Time	Username	Problem	Language	Result	Execution time	Memory
1088480		Icelast	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	503 ms	12048 KiB

ho_t4

#include <iostream>
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll maxn = 201, INF = 4e18+9;
struct edge{
    ll u, v, c, d, id;
};
vector<ll> dijkstra(int s, vector<vector<edge>> &adj, edge e){
    int ban = e.id;
    adj[e.v].push_back({e.v, e.u, e.c, e.d, -1});
    int n = adj.size();
    vector<ll> dist(n+1, INF);
    dist[s] = 0;
    vector<bool> vis(n+1, false);
    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq;
    pq.push({0, s});
    while(!pq.empty()){
        ll d_u = pq.top().first;
        int u = pq.top().second;
        pq.pop();
        if(vis[u]){
            continue;
        }
        vis[u] = true;
        for(auto it : adj[u]){
            int v = it.v, id = it.id;
            ll w = it.c;

            if(vis[v] || ban == id) continue;
            if(dist[v] > d_u+w){
                dist[v] = d_u+w;
                pq.push({dist[v], v});
            }
        }
    }
    adj[e.v].pop_back();
    return dist;
}
vector<ll> dijkstra_trace(int s, int t, int m, vector<vector<edge>> &adj){
    vector<ll> res(m+1, 0);
    int n = adj.size();
    vector<ll> dist(n+1, INF);
    vector<pair<int, int>> pa(n+1);
    dist[s] = 0;
    vector<bool> vis(n+1, false);
    priority_queue<pair<ll, ll>, vector<pair<ll, ll>>, greater<pair<ll, ll>>> pq;
    pq.push({0, s});
    while(!pq.empty()){
        ll d_u = pq.top().first;
        int u = pq.top().second;
        pq.pop();
        if(vis[u]){
            continue;
        }
        vis[u] = true;
        for(auto it : adj[u]){
            int v = it.v;
            ll w = it.c;
            if(vis[v]) continue;
            if(dist[v] > d_u+w){
                dist[v] = d_u+w;
                pa[v] = {u, it.id};
                pq.push({dist[v], v});
            }
        }
    }
    if(dist[t] == INF) return res;
    while(t != s){
        res[pa[t].second] = 1;
        t = pa[t].first;
    }
    return res;
}
void solve(){
    int n, m;
    cin >> n >> m;
    vector<vector<edge>> adj(n+1), adj_rev(n+1);
    vector<edge> e(1);
    for(int i = 1; i <= m; i++){
        int u, v;
        ll c, d;
        cin >> u >> v >> c >> d;
        e.push_back({u, v, c, d, i});
        adj[u].push_back({u, v, c, d, i});
        adj_rev[v].push_back({v, u, c, d, i});
    }
    edge null = {0, 0, INF, INF, -1};
    vector<ll> dist_1f = dijkstra(1, adj, null),
               dist_1b = dijkstra(n, adj_rev, null),

               dist_nf = dijkstra(n, adj, null),
               dist_nb = dijkstra(1, adj_rev, null);
    vector<ll> bamboo_1 = dijkstra_trace(1, n, m, adj),
               bamboo_n = dijkstra_trace(n, 1, m, adj);
    auto solvefor = [&](int s, int t, vector<ll> dist_f, vector<ll> dist_b, vector<ll> bamboo) -> vector<ll>{
        vector<ll> res(m+1);
        for(int i = 1; i <= m; i++){
            if(bamboo[i]){
                vector<ll> a = dijkstra(s, adj, e[i]);
                res[i] = a[t];
            }else{
                res[i] = min(dist_f[t], dist_f[e[i].v]+e[i].c+dist_b[e[i].u]);
            }
        }
        return res;
    };
    vector<ll> res_1 = solvefor(1, n, dist_1f, dist_1b, bamboo_1),
               res_n = solvefor(n, 1, dist_nf, dist_nb, bamboo_n);

    ll ans = dist_1f[n] + dist_nf[1];
    for(int i = 1; i <= m; i++){
        ans = min(ans, res_1[i] + res_n[i] + e[i].d);
    }
    if(ans >= INF) ans = -1;
    cout << ans;
}
int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    solve();
}

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