Submission #1317983

#	Time	Username	Problem	Language	Result	Execution time	Memory
1317983		mantaggez	Commuter Pass (JOI18_commuter_pass)	C++20	100 / 100	286 ms	32660 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

#define ll long long 
#define pii pair<ll, ll>

const int nx = 1e5+5;
const ll INF = 1e18;

int n, m, s, t, U, V;
vector<pii> adj[nx], dag[nx], revdag[nx];
vector<ll> distu, distv, dists, distt;
priority_queue<pii, vector<pii>, greater<pii>> pq;

void dijkstra(int src, vector<ll>& d)
{
    vector<ll> dist(nx, INF);
    dist[src] = 0;
    pq.push({0, src});
    while(!pq.empty())
    {
        auto [cw, u] = pq.top();
        pq.pop();
        if(cw > dist[u]) continue;
        for(auto [v, nw] : adj[u])
        {
            if(dist[v] > dist[u] + nw)
            {
                dist[v] = dist[u] + nw;
                pq.push({dist[v], v});
            }
        }
    }

    d = dist;
}

vector<ll> mindist(int src, vector<pii> DAG[])
{
    vector<ll> mn(nx, INF);
    mn[src] = distv[src];
    pq.push({0, src});    
    while(!pq.empty())
    {
        auto [cw, u] = pq.top();
        pq.pop();
        if(cw > dists[u]) continue;  
        for(auto [v, nw] : DAG[u])
        {
            if(mn[u] < mn[v])
            {
                mn[v] = mn[u];
                pq.push({dists[v], v});
            }
            mn[v] = min(mn[v], distv[v]);
        }
    }
    return mn;
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin >> n >> m >> s >> t >> U >> V;
    for(int i=0;i<m;i++)
    {
        ll a, b, c;
        cin >> a >> b >> c;
        adj[a].push_back({b, c});
        adj[b].push_back({a, c});
    }

    dijkstra(U, distu);
    dijkstra(V, distv);
    dijkstra(s, dists);
    dijkstra(t, distt);

    ll D = dists[t];

    for(int u=1;u<=n;u++)
        for(auto [v, w] : adj[u])
            if(dists[u] + w + distt[v] == D)
                dag[u].push_back({v, w});

    for(int u=1;u<=n;u++)
        for(auto [v, w] : dag[u])
            revdag[v].push_back({u, w});

    vector<ll> minToV = mindist(s, dag);
    vector<ll> minToV2 = mindist(t, revdag);

    for(int i=1;i<=n;i++)
        minToV[i] = min(minToV[i], minToV2[i]);

    ll res = distu[V];

    for(int i=1;i<=n;i++)
    {
        if(dists[i] + distt[i] == D)
            res = min(res, distu[i] + minToV[i]);
    }

    cout << res ;

    return 0;
}

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