Submission #1280162

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280162		peanut	Commuter Pass (JOI18_commuter_pass)	C++20	100 / 100	296 ms	21948 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define fi first
#define se second
#define pb push_back
#define mp make_pair

vector<int> dx = {0, 0, 1, -1};
vector<int> dy = {1, -1, 0, 0};

const int maxn = 1e5 + 5;
const int MOD = 1e9 + 7;
const ll INF = 0x3f3f3f3f3f3f3f3f;

int n, m;
vector<pii> adj[maxn];

void dijkstra(int s, vector<ll> &dist)
{
    dist[s] = 0;
    priority_queue<pair<ll, int>> pq;
    pq.push({0, s});
    while (!pq.empty())
    {
        ll d = -pq.top().fi;
        int u = pq.top().se;
        pq.pop();
        if (d != dist[u]) continue;
        for (auto [v, w] : adj[u])
        {
            if (d + w < dist[v])
            {
                dist[v] = d + w;
                pq.push({-dist[v], v});
            }
        }
    }
}

int main()
{
    ios::sync_with_stdio(false); cin.tie(0);
    //freopen(".INP", "r", stdin);
    //freopen(".OUT", "w", stdout);
    int s, t, u, v; cin >> n >> m >> s >> t >> u >> v;
    vector<tuple<int, int, int>> roads;
    for (int i = 1; i <= m; ++i)
    {
        int a, b, w; cin >> a >> b >> w;
        adj[a].pb({b, w});
        adj[b].pb({a, w});
        roads.pb(make_tuple(a, b, w));
    }

    vector<ll> distS(n+1, INF), distT(n+1, INF), distU(n+1, INF), distV(n+1, INF);
    dijkstra(s, distS); dijkstra(t, distT); dijkstra(u, distU); dijkstra(v, distV);

    vector<vector<int>> dag(n+1);
    vector<int> nodes;
    for (auto [i, j, w] : roads)
    {
        if (distS[i] != INF && distT[j] != INF && distS[i] + distT[j] + w == distS[t]) dag[i].pb(j);
        if (distS[j] != INF && distT[i] != INF && distS[j] + distT[i] + w == distS[t]) dag[j].pb(i);
    }
    for (int i = 1; i <= n; ++i) if (distS[i] + distT[i] == distS[t]) nodes.pb(i);
    sort(all(nodes), [&](int a, int b) {return distS[a] < distS[b];});

    ll ans = distU[v];
    vector<ll> dp(n+1, INF);
    vector<ll> dp2(n+1, INF);
    for (auto i : nodes)
    {
        dp[i] = min(dp[i], distU[i]);
        dp2[i] = min(dp2[i], distV[i]);
        ans = min({ans, dp[i] + distV[i], dp2[i] + distU[i]});
        for (auto j : dag[i])
        {
            dp[j] = min(dp[j], dp[i]);
            dp2[j] = min(dp2[j], dp2[i]);
        }
    }
    cout << ans;
    return 0;
}

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