Submission #367520

#	Time	Username	Problem	Language	Result	Execution time	Memory
367520		arujbansal	Relay Marathon (NOI20_relaymarathon)	C++17	17 / 100	6055 ms	112868 KiB

RelayMarathon

#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <array>
#include <stack>
#include <queue>
#include <random>
#include <numeric>
#include <functional>
#include <chrono>
#include <utility>
#include <iomanip>
#include <assert.h>

using namespace std;

void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail>
void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)

#define rng_init mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
#define rng_seed(x) mt19937 rng(x)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
// #define int long long

rng_init;

const int MXN = 1e5 + 5, INF = 1e9 + 5;
int N, M, K;
vector<pair<int, int>> g[MXN];
vector<array<int, 3>> edges;

void dijkstra(const vector<int> &src, vector<int> &dist, vector<int> &par) {
    priority_queue<pair<int, int>, vector<pair<int, int>>, greater<>> pq;
    
    for (const auto &x : src) {
        dist[x] = 0;
        pq.emplace(0, x);
    }

    for (int i = 0; i < N; i++)
        par[i] = i;

    while (!pq.empty()) {
        auto cur = pq.top();
        pq.pop();

        int u = cur.second, cur_dist = cur.first;
        if (cur_dist != dist[u]) continue;

        for (const auto &[v, wt] : g[u]) {
            int new_dist = cur_dist + wt;

            if (new_dist < dist[v]) {
                dist[v] = new_dist;
                pq.emplace(new_dist, v);

                par[v] = par[u];
            }
        }
    }
}

int closest_pair(const vector<int> &dist, const vector<int> &par) {
    int pair_dist = INF;

    for (const auto &[u, v, wt] : edges) {
        if (par[u] == par[v]) continue;

        pair_dist = min(pair_dist, dist[u] + wt + dist[v]);
    }

    return pair_dist;
}

void solve() {
    cin >> N >> M >> K;

    for (int i = 0; i < M; i++) {
        int u, v, w;
        cin >> u >> v >> w;
        u--, v--;

        edges.push_back({u, v, w});

        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }

    vector<int> special(K);
    for (auto &x : special) {
        cin >> x;
        x--;
    }

    int ans = INF;

    for (int iter = 0; iter < 50; iter++) {
        vector<int> src[2];

        for (const auto &x : special)
            src[rng() % 2].push_back(x);

        vector<int> dist1(N, INF), dist2(N, INF);
        vector<int> par1(N), par2(N);

        dijkstra(src[0], dist1, par1);
        dijkstra(src[1], dist2, par2);

        ans = min(ans, closest_pair(dist1, par1) + closest_pair(dist2, par2));
    }

    cout << ans;
}

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

    int TC = 1;
    // cin >> TC;
    while (TC--) solve();
}

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 0 / 25
• Subtask 4: 0 / 58