Submission #964337

#	Time	Username	Problem	Language	Result	Execution time	Memory
964337		Akshat369	Olympic Bus (JOI20_ho_t4)	C++17	100 / 100	434 ms	6664 KiB

ho_t4

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

#define int long long
#define INF 1e18
#define endl '\n'
const int N = 205;

struct node {
    int u, v, c, d;
};

multiset<pair<int, int>> graph[N];

vector<int> dijkstra(int src) {
    vector<int> dist(N, INF);
    vector<bool> vis(N, false);

    dist[src] = 0;
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> pq;
    pq.push({0, src});

    while (!pq.empty()) {
        int u = pq.top().second;
        pq.pop();
        if (vis[u]) continue;
        vis[u] = true;

        for (auto& [v, weight] : graph[u]) {
            if (dist[v] > dist[u] + weight) {
                dist[v] = dist[u] + weight;
                pq.push({dist[v], v});
            }
        }
    }
    return dist;
}

void solve() {
    int n, m;
    cin >> n >> m;
    vector<node> edges(m);
    for (int i = 0; i < m; ++i) {
        cin >> edges[i].u >> edges[i].v >> edges[i].c >> edges[i].d;
        graph[edges[i].u].insert({edges[i].v, edges[i].c});
    }

    vector<vector<int>> dist(n + 1, vector<int>(n + 1, INF));
    for (int i = 1; i <= n; ++i) dist[i][i] = 0;
    for (auto& e : edges) {
        dist[e.u][e.v] = min(dist[e.u][e.v], e.c);
    }

    for (int k = 1; k <= n; ++k) {
        for (int i = 1; i <= n; ++i) {
            for (int j = 1; j <= n; ++j) {
                dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
            }
        }
    }

    int ans = dist[1][n] + dist[n][1];
    for (auto& e : edges) {
        int u = e.u, v = e.v;
        if (min(dist[1][n], dist[1][v] + e.c + dist[u][n]) + min(dist[n][1], dist[n][v] + e.c + dist[u][1]) + e.d >= ans) continue;

        graph[u].erase(graph[u].find({v, e.c}));
        graph[v].insert({u, e.c});

        auto dis1 = dijkstra(1);
        auto dis2 = dijkstra(n);
        ans = min(ans, dis1[n] + dis2[1] + e.d);

        graph[v].erase(graph[v].find({u, e.c}));
        graph[u].insert({v, e.c});
    }

    if (ans >= INF) cout << -1 << endl;
    else cout << ans << endl;
}

int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    solve();

    return 0;
}

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