Submission #812207

#	Time	Username	Problem	Language	Result	Execution time	Memory
812207		vjudge1	Olympic Bus (JOI20_ho_t4)	C++17	5 / 100	177 ms	2980 KiB

ho_t4

#include<bits/stdc++.h>

using namespace std;
using ll = long long;

const int N = 1000;
const int M = 100000;
const ll INF = 1e18;

int n, m;
vector<pair<int, int>> g[N], g0[N];
ll C[M], D[M];
pair<int, int> edges[M];

vector<ll> dijkstra(int s, vector<pair<int, int>> g[]) {
    vector<ll> dist(n + 1, INF);
    dist[s] = 0;
    set<pair<ll, int>> st; 
    for(int i = 1; i <= n; i++) 
        st.insert({dist[i], i});
    while(!st.empty()) {
        s = st.begin()->second;
        st.erase(st.begin());
        for(auto [to, i] : g[s]) {
            if(dist[to] > dist[s] + C[i]) {
                st.erase({dist[to], to});
                dist[to] = dist[s] + C[i];
                st.insert({dist[to], to});
            }
        }
    }
    return dist;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    cin >> n >> m;
    for(int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        edges[i] = {u, v};
        cin >> C[i] >> D[i];
        g[u].push_back({v, i});
        g0[v].push_back({u, i});
    }
    bool subtask2 = 1;
    for(int i = 0; i < m; i += 2) 
        subtask2 &= (edges[i] == edges[i + 1] && C[i] == C[i + 1]);
    if(subtask2) {
        auto d1 = dijkstra(1, g);
        auto dn = dijkstra(n, g);
        auto e1 = dijkstra(1, g0);
        auto en = dijkstra(n, g0);
        ll res = d1[n] + dn[1];
        for(int i = 0; i < m; i++) {
            auto [u, v] = edges[i];
            res = min(res, d1[u] + en[v] + dn[1] + C[i] + D[i]);
            res = min(res, dn[v] + e1[u] + d1[n] + C[i] + D[i]);
        }
        if(res >= INF) res = -1;
        cout << res;
        return 0;
    }
    if(m <= 1000) {
        ll res = dijkstra(1, g)[n] + dijkstra(n, g)[1];
        for(int i = 0; i < m; i++) {
            auto [u, v] = edges[i];
            g[u].erase(find(g[u].begin(), g[u].end(), make_pair(v, i)));
            g[v].push_back({u, i});
            res = min(res, dijkstra(1, g)[n] + dijkstra(n, g)[1] + D[i]);
            g[u].push_back({v, i});
            g[v].erase(find(g[v].begin(), g[v].end(), make_pair(u, i)));
        }
        if(res >= INF) res = -1;
        cout << res;
        return 0;
    }
}

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