Submission #745890

#	Time	Username	Problem	Language	Result	Execution time	Memory
745890		vjudge1	Cities (BOI16_cities)	C++17	14 / 100	330 ms	18740 KiB

cities

#include <climits>
#include <iostream>
#include <queue>
#include <vector>

using namespace std;

using ll = long long;

struct edge {
    int to;
    ll weight;

    bool operator >(edge const& rhs) const {
        return weight > rhs.weight;
    }
};

vector<ll> dijkstra(vector<vector<edge>> const& graph, int const start) {
    priority_queue<edge, vector<edge>, greater<edge>> pq;
    vector<ll> dist(graph.size(), LLONG_MAX / 3);

    dist[start] = 0;
    pq.push({ start, 0 });

    while (!pq.empty()) {
        auto const [cur, cur_dist] = pq.top();
        pq.pop();

        if (cur_dist != dist[cur])
            continue;

        for (auto const& [neigh, weight] : graph[cur]) {
            ll const new_dist = cur_dist + weight;

            if (new_dist < dist[neigh]) {
                dist[neigh] = new_dist;
                pq.push({ neigh, new_dist });
            }
        }
    }

    return dist;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, k, m;
    cin >> n >> k >> m;

    vector<int> important(k);

    for (int& x : important) {
        cin >> x;
        x--;
    }
    

    vector<vector<edge>> graph(n);

    for (int i = 0; i < m; i++) {
        int u, v;
        ll w;
        cin >> u >> v >> w;
        u--; v--;
        
        graph[u].push_back({ v, w });
        graph[v].push_back({ u, w });
    }

    vector<vector<ll>> dist(k);

    for (int i = 0; i < k; i++)
        dist[i] = dijkstra(graph, important[i]);
    
    if (k == 2) {
        cout << dist[0][important[1]] << "\n";
    }
    else {
        ll min_dist = LLONG_MAX / 3;

        for (int i = 0; i < n; i++) {
            ll const cur_dist = dist[0][i] + dist[1][i] + dist[2][i];

            min_dist = min(min_dist, cur_dist);
        } 

        cout << min_dist << "\n";
    }
}

• Subtask 1: 0 / 22
• Subtask 2: 14 / 14
• Subtask 3: 0 / 15
• Subtask 4: 0 / 23
• Subtask 5: 0 / 26