Submission #519504

#	Time	Username	Problem	Language	Result	Execution time	Memory
519504		Jarif_Rahman	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	325 ms	39552 KiB

commuter_pass

#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;
const ll inf = 1e16;

vector<ll> dijsktra(vector<vector<pair<int, ll>>> v, int s){
    int n = v.size();

    vector<ll> dis(n, inf);
    vector<bool> bl(n, 0);
    priority_queue<pair<ll, int>> pq;

    dis[s] = 0;
    pq.push({0, s});

    while(!pq.empty()){
        int nd = pq.top().sc;
        pq.pop();
        if(bl[nd]) continue;
        bl[nd] = 1;

        for(auto [x, w]: v[nd]) if(dis[nd]+w < dis[x]){
            dis[x] = dis[nd]+w;
            pq.push({-dis[x], x});
        }
    }

    return dis;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n, m; cin >> n >> m;
    int S, T, U, V; cin >> S >> T >> U >> V; S--, T--, U--, V--;

    vector<vector<pair<int, ll>>> v(n);

    for(int i = 0; i < m; i++){
        int a, b; ll w; cin >> a >> b >> w; a--, b--;
        v[a].pb({b, w});
        v[b].pb({a, w});
    }

    vector<ll> ds = dijsktra(v, S), du = dijsktra(v, U), dv = dijsktra(v, V);

    ll ans = du[V];

    vector<pair<ll, ll>> dp1(n, {inf, inf}), dp2(n, {inf, inf});

    function<pair<pair<ll, ll>, pair<ll, ll>>(int)> DP = [&](int nd){
        if(dp1[nd].f != inf){
            return make_pair(dp1[nd], dp2[nd]);
        }
        ans = min(ans, du[nd]+dv[nd]);
        for(auto [x, w]: v[nd]){
            if(ds[x]+w != ds[nd]) continue;
            auto [p1, p2] = DP(x);
            if(p1.f < dp1[nd].f) dp1[nd] = p1;
            if(p2.sc < dp2[nd].sc) dp2[nd] = p2;
        }

        dp1[nd].f = min(dp1[nd].f, du[nd]);
        dp1[nd].sc = min(dp1[nd].sc, dv[nd]);
        dp2[nd].f = min(dp2[nd].f, du[nd]);
        dp2[nd].sc = min(dp2[nd].sc, dv[nd]);

        ans = min(ans, dp1[nd].f+dp1[nd].sc);
        ans = min(ans, dp2[nd].f+dp2[nd].sc);

        return make_pair(dp1[nd], dp2[nd]);
    };

    DP(T);

    cout << ans << "\n";
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45