Submission #1267459

#	Time	Username	Problem	Language	Result	Execution time	Memory
1267459		gay	Olympic Bus (JOI20_ho_t4)	C++20	37 / 100	1096 ms	11852 KiB

ho_t4

#include <bits/stdc++.h>
#include <experimental/random>
#include <random>

using namespace std;
using ll = long long;
using ld = long double;

const ll INF = 2e18, MOD = 998244353;

void solve();

signed main() {
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    ll q = 1;
    //cin >> q;
    while (q--) {
        solve();
    }
}

struct e {
    ll v, c, d, id;
};

ll n, m;

vector<vector<bool>> calc(vector<vector<e>>& g, ll s) {
    vector<pair<ll, ll>> pred(n, {-1, -1});
    vector<ll> dp(n, INF);
    dp[s] = 0;
    set<pair<ll, ll>> dj;
    dj.insert({0, s});
    while (!empty(dj)) {
        auto [w, u] = *dj.begin();
        dj.erase(dj.begin());
        for (auto [v, c, d, id] : g[u]) {
            if (dp[v] > w + c) {
                pred[v] = {u, id};
                dj.erase({dp[v], v});
                dp[v] = w + c;
                dj.insert({dp[v], v});
            }
        }
    }

    vector<vector<bool>> ans(n, vector<bool>(m));
    for (int i = 0; i < n; i++) {
        ll t = i;
        while (pred[t].second != -1) {
            ans[i][pred[t].second] = 1;
            t = pred[t].first;
        }
    }

    return ans;
}

vector<ll> cost(vector<vector<e>>& g, ll s) {
    vector<ll> dp(n, INF);
    dp[s] = 0;
    set<pair<ll, ll>> dj;
    dj.insert({0, s});
    while (!empty(dj)) {
        auto [w, u] = *dj.begin();
        dj.erase(dj.begin());
        for (auto [v, c, d, id] : g[u]) {
            if (dp[v] > w + c) {
                dj.erase({dp[v], v});
                dp[v] = w + c;
                dj.insert({dp[v], v});
            }
        }
    }
    return dp;
}

void rev_ed(ll u, ll v, ll idx, vector<vector<e>>& g) {
    vector<e> x = g[u];
    g[u].clear();
    e hv{};
    for (auto ed : x) {
        if (ed.id != idx) {
            g[u].push_back(ed);
        } else {
            hv = ed;
        }
    }
    g[v].push_back({u, hv.c, hv.d, hv.id});
}

void del_ed(ll u, ll idx, vector<vector<e>>& g) {
    vector<e> x = g[u];
    g[u].clear();
    for (auto ed : x) {
        if (ed.id != idx) {
            g[u].push_back(ed);
        }
    }
}


void solve() {
    cin >> n >> m;
    vector<vector<e>> g(n), rev_g(n);
    vector<e> edges;
    for (int i = 0; i < m; i++) {
        ll u, v, c, d;
        cin >> u >> v >> c >> d;
        u--, v--;
        edges.push_back({u, v, c, d});
        g[u].push_back({v, c, d, i});
        rev_g[v].push_back({u, c, d, i});
    }

    vector<vector<bool>> dp1 = calc(g, 0);
    vector<vector<bool>> dp2 = calc(rev_g, n - 1);
    vector<vector<bool>> dp3 = calc(g, n - 1);
    vector<vector<bool>> dp4 = calc(rev_g, 0);

    vector<ll> c1 = cost(g, 0);
    vector<ll> c2 = cost(rev_g, n - 1);
    vector<ll> c3 = cost(g, n - 1);
    vector<ll> c4 = cost(rev_g, 0);

    ll ans = c1[n - 1] + c3[0];

    for (int i = 0; i < m; i++) {
        auto [u, v, w, d] = edges[i];
        rev_ed(u, v, i, g);
        rev_ed(v, u, i, rev_g);

        ll p1 = c1[n - 1], p2 = c3[0];
        if (dp1[n - 1][i]) {
            p1 = cost(g, 0)[n - 1];
        }
        if (dp3[0][i]) {
            p2 = cost(g, n - 1)[0];
        }

        ll cnt = c1[v] + w;
        if (dp1[v][i]) {
            del_ed(u, i, g);
            cnt = cost(g, 0)[v] + w;
            g[u].push_back({v, w, d, i});
        }
        ll cnt2 = c2[u];
        if (dp2[u][i]) {
            del_ed(v, i, rev_g);
            cnt2 = cost(rev_g, n - 1)[u];
            rev_g[v].push_back({u, w, d, i});
        }
        p1 = min(p1, cnt + cnt2);

        cnt = c3[v] + w;
        if (dp3[v][i]) {
            del_ed(u, i, g);
            cnt = cost(g, n - 1)[v] + w;
            g[u].push_back({v, w, d, i});
        }
        cnt2 = c4[u];
        if (dp4[u][i]) {
            del_ed(v, i, rev_g);
            cnt2 = cost(rev_g, 0)[u];
            rev_g[v].push_back({u, w, d, i});
        }
        p2 = min(p2, cnt + cnt2);

        ans = min(ans, p1 + p2 + d);
        rev_ed(v, u, i, g);
        rev_ed(u, v, i, rev_g);
    }

    if (ans >= INF) {
        cout << -1;
        return;
    }

    cout << ans;
}

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