Submission #373266

#	Time	Username	Problem	Language	Result	Execution time	Memory
373266		ja_kingy	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	440 ms	28504 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll,ll> pii;

const ll MXN = 1e5+1, INF = 1e18;
ll n,m,s,t,u,v,disS[MXN],disU[MXN],disV[MXN],ans;
vector<pii> adj[MXN];
pii cache[MXN][2];

void dijk(int s, ll* dis) {
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    fill(dis, dis+n+1, INF);
    pq.emplace(0, s);
    dis[s] = 0;
    while (pq.size()) {
        pii u = pq.top(); pq.pop();
        if (u.first != dis[u.second]) continue;
        for (pii e: adj[u.second]) {
            ll nw = e.second + u.first;
            if (nw < dis[e.first]) {
                dis[e.first] = nw;
                pq.emplace(nw, e.first);
            }            
        }
    }
}

pii dp(int u, int dir) {
    if (cache[u][dir].first < 0) {
        cache[u][dir] = {INF, INF};
        for (pii e: adj[u]) {
            ll nw = disS[u] + (dir ? e.second : -e.second);
            if (nw == disS[e.first]) {
                pii res = dp(e.first, dir);
                cache[u][dir].first = min(cache[u][dir].first, res.first);
                cache[u][dir].second = min(cache[u][dir].second, res.second);
            }            
        }
        if (cache[u][dir].first != INF || u == (dir ? t : s)) {
            cache[u][dir].first = min(cache[u][dir].first, disU[u]);
            cache[u][dir].second = min(cache[u][dir].second, disV[u]);            
        }
    }
    return cache[u][dir];
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m >> s >> t >> u >> v;
    for (int i = 0,a,b,c; i < m; ++i) {
        cin >> a >> b >> c;
        adj[a].emplace_back(b,c);
        adj[b].emplace_back(a,c);
    }
    dijk(s, disS);
    dijk(u, disU);
    dijk(v, disV);
    fill(&cache[0][0], &cache[n+1][0], make_pair(-1,-1));
    ans = disU[v];
    for (int i = 1; i <= n; ++i) {
        pii be = dp(i,1), ab = dp(i,0);
        ans = min({ans, ab.first + be.second, ab.second + be.first});
    }
    cout << ans;
}

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