Submission #757573

#	Time	Username	Problem	Language	Result	Execution time	Memory
757573		Desh03	Olympic Bus (JOI20_ho_t4)	C++17	0 / 100	1078 ms	3796 KiB

ho_t4

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

const long long INF = 1e18;
int n;
vector<multiset<pair<int, int>>> g;

void djikstra(int src, vector<long long> &sp) {
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
    pq.push({sp[src] = 0, src});
    vector<bool> vis(n);
    while (pq.size()) {
        int u = pq.top().second;
        pq.pop();
        if (vis[u]) continue;
        vis[u] = 1;
        for (auto [v, w] : g[u]) {
            if (sp[u] + w < sp[v])
                sp[v] = sp[u] + w, pq.push({sp[v], v});
        }
    }
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int m;
    cin >> n >> m;
    g.resize(n);
    vector<long long> sp1, sp2;
    vector<vector<long long>> dp(n, vector<long long> (n, INF));
    vector<tuple<int, int, int, int>> edges;
    for (int i = 0; i < m; i++) {
        int u, v, c, d;
        cin >> u >> v >> c >> d;
        --u, --v;
        g[u].insert({v, c});
        dp[u][v] = min(dp[u][v], (long long) c);
        edges.push_back({u, v, c, d});
    }
    for (int i = 0; i < n; i++) dp[i][i] = 0;
    for (int k = 0; k < n; k++)
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
    long long ans = dp[0][n - 1] + dp[n - 1][0];
    for (auto [u, v, c, d] : edges) {
        if (u && v && u != n - 1 && v != n - 1) {
            ans = min(ans, dp[0][v] + dp[u][n - 1] + dp[n - 1][0] + c + d);
            ans = min(ans, dp[0][n - 1] + dp[n - 1][v] + dp[u][0] + c + d);
        } else {
            g[u].erase(g[u].find({v, c}));
            g[v].insert({u, c});
            sp1 = sp2 = vector<long long> (n, INF);
            djikstra(0, sp1), djikstra(n - 1, sp2);
            ans = min(ans, sp1[n - 1] + sp2[0] + d);
            g[v].erase(g[v].find({u, c}));
            g[u].insert({v, c});
        }
    }
    cout << (ans == INF ? -1 : ans) << '\n';
}

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