Submission #375673

#	Time	Username	Problem	Language	Result	Execution time	Memory
375673		valerikk	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	435 ms	22680 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;

const ll INF = (ll)1e18 + 100;

struct Edge {
    int a, b, c;
};

vector<ll> get_dists(int n, int st, const vector<vector<pair<int, int>>> &g) {
    vector<ll> dist(n, INF);
    dist[st] = 0;
    priority_queue<pair<ll, int>, vector<pair<ll, int>>, greater<pair<ll, int>>> pq;
    auto psh = [&](int v) {
        pq.push({dist[v], v});
    };
    psh(st);
    while (!pq.empty()) {
        auto [dst, v] = pq.top();
        pq.pop();
        if (dst != dist[v]) continue;
        for (const auto& [u, w] : g[v]) {
            if (dist[v] + w < dist[u]) {
                dist[u] = dist[v] + w;
                psh(u);
            }
        }
    }
    for (int i = 0; i < n; ++i) assert(dist[i] < INF);
    return dist;
}

int main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
#endif
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, s, t, u, v;
    cin >> n >> m >> s >> t >> u >> v;
    --s;
    --t;
    --u;
    --v;
    vector<Edge> ed(m);
    vector<vector<pair<int, int>>> g(n);
    for (int i = 0; i < m; ++i) {
        cin >> ed[i].a >> ed[i].b >> ed[i].c;
        --ed[i].a;
        --ed[i].b;
        g[ed[i].a].push_back({ed[i].b, ed[i].c});
        g[ed[i].b].push_back({ed[i].a, ed[i].c});
    }
    auto ds = get_dists(n, s, g);
    auto dt = get_dists(n, t, g);
    auto du = get_dists(n, u, g);
    auto dv = get_dists(n, v, g);
    auto slv = [&]() {
        vector<pair<ll, int>> srt;
        for (int i = 0; i < n; ++i) srt.push_back({ds[i], i});
        sort(srt.begin(), srt.end());
        vector<ll> mn(n);
        for (int i = 0; i < n; ++i) mn[i] = dv[i];
        ll ret = INF;
        for (int i = n - 1; i >= 0; --i) {
            int curv = srt[i].second;
            for (auto [curu, w] : g[curv]) {
                if (ds[curv] + dt[curu] + w == ds[t]) {
                    mn[curv] = min(mn[curv], mn[curu]);
                }
            }
            ret = min(ret, du[curv] + mn[curv]);
        }
        return ret;
    };
    ll ans = slv();
    swap(u, v);
    swap(du, dv);
    ans = min(ans, slv());
    cout << ans << endl;
    return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45