Submission #857440

#	Time	Username	Problem	Language	Result	Execution time	Memory
857440		asdasdqwer	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	299 ms	32136 KiB

commuter_pass

// #define FMT_HEADER_ONLY
// #include <fmt/ranges.h>
#include <bits/stdc++.h>
using namespace std;

#define int int64_t
#define pii pair<int, int>

vector<int> dijkstra(int source, vector<vector<pii>> &g) {
    int n = g.size();
    vector<int> dis(n, 1e16);
    dis[source] = 0;

    priority_queue<pii> pq;
    for (int i=0;i<n;i++) {
        pq.push({-dis[i], i});
    }

    vector<bool> vis(n, false);

    while (!pq.empty()) {
        pii t = pq.top();pq.pop();
        int node = t.second;
        if (vis[node]) continue;
        vis[node] = true;

        for (pii &x:g[node]) {
            if (dis[node] + x.second < dis[x.first]) {
                dis[x.first] = dis[node] + x.second;
                pq.push({-dis[x.first], x.first});
            }
        }
    }

    return dis;
}

void dfs(int node, vector<int> &vis, vector<int> &topo, vector<vector<int>> &g) {
    vis[node] = 1;
    for (int x:g[node]) {
        if (vis[x] == 0) {
            dfs(x, vis, topo, g);
        }
    }

    vis[node] = 2;
    topo.push_back(node);
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, m;cin>>n>>m;

    int s, t;cin>>s>>t;s--;t--;
    int u, v;cin>>u>>v;u--;v--;

    vector<vector<pii>> g(n);

    for (int i=0;i<m;i++) {
        int a, b, c;cin>>a>>b>>c;
        a--;b--;
        g[a].push_back({b, c});
        g[b].push_back({a, c});
    }

    vector<int> disFromS = dijkstra(s, g);

    vector<vector<int>> dag(n);
    queue<int> q;
    q.push(t);
    vector<bool> proc(n, false);
    proc[t] = true;

    while (!q.empty()) {
        int tp = q.front();q.pop();
        for (pii &x:g[tp]) {
            if (disFromS[tp] == disFromS[x.first] + x.second) {
                dag[x.first].push_back(tp);
                
                if (!proc[x.first]) {
                    proc[x.first] = true;
                    q.push(x.first);
                }
            }
        }
    }

    vector<int> vis(n, 0), topo;
    
    for (int i=0;i<n;i++) {
        if (vis[i] == 0 && dag[i].size()) {
            dfs(i, vis, topo, dag);
        }
    }

    reverse(topo.begin(), topo.end());

    vector<int> disToU = dijkstra(u, g), disToV = dijkstra(v, g);
    int mn = disToV[u];

    vector<int> minGet(n, 1e16);

    for (int i=0;i<topo.size();i++) {
        int elem = topo[i];

        if (i == 0) {
            minGet[elem] = disToU[elem];
            mn = min(mn, minGet[elem] + disToV[elem]);
        }

        mn = min(mn, minGet[elem] + disToV[elem]);

        for (int x:dag[elem]) {
            minGet[x] = min(minGet[x], min(minGet[elem], disToU[x]));
            mn = min(mn, minGet[x] + disToV[x]);
        }
    }

    vector<vector<int>> rev(n);
    for (int i=0;i<n;i++) {
        for (int x:dag[i]) {
            rev[x].push_back(i);
        }
    }

    vis = vector<int>(n, 0);
    vector<int> newTopo;
    for (int i=0;i<n;i++) {
        if (vis[i] == 0 && rev[i].size()) {
            dfs(i, vis, newTopo, rev);
        }
    }

    minGet = vector<int>(n, 1e16);
    // cerr << (newTopo[0] == t) << "\n";
    // fmt::print("{}\n", newTopo);

    reverse(newTopo.begin(), newTopo.end());

    for (int i=0;i<(int)newTopo.size();i++) {
        int elem = newTopo[i];

        if (i == 0) {
            minGet[elem] = disToU[elem];
        }

        mn = min(mn, minGet[elem] + disToV[elem]);

        for (int x:rev[elem]) {
            minGet[x] = min(minGet[x], min(minGet[elem], disToU[x]));
            mn = min(mn, minGet[x] + disToV[x]);
        }
    }

    cout << mn << "\n";
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:105:19: warning: comparison of integer expressions of different signedness: 'int64_t' {aka 'long int'} and 'std::vector<long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  105 |     for (int i=0;i<topo.size();i++) {
      |                  ~^~~~~~~~~~~~

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