Submission #517013

#	Time	Username	Problem	Language	Result	Execution time	Memory
517013		nighty	Commuter Pass (JOI18_commuter_pass)	C++14	55 / 100	2067 ms	20884 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

vector<int> last;

set<pair<int, int>> choosenE;

vector<long long> dijkstra(int start, vector<vector<pair<int, int>>>& g) {
    int n = g.size();
    vector<long long> d(n, numeric_limits<long long>::max());
    last.assign(n, -1);
    d[start] = 0;
    set<pair<long long, int>> s; // {d[i], i}
    s.insert({0, start});
    while (!s.empty()) {
        int i = s.begin()->second;
        s.erase(s.begin());
        for (auto [j, w] : g[i]) {
            if (d[i] + w < d[j]) {
                s.erase({d[j], j});
                d[j] = d[i] + w;
                last[j] = i;
                s.insert({d[j], j});
            }
        }
    }
    return d;
}

vector<long long> dijkstra2(int start, vector<vector<pair<int, int>>>& g) {
    int n = g.size();
    vector<long long> d(n, numeric_limits<long long>::max());
    last.assign(n, -1);
    d[start] = 0;
    set<pair<long long, int>> s; // {d[i], i}
    s.insert({0, start});
    while (!s.empty()) {
        int i = s.begin()->second;
        s.erase(s.begin());
        for (auto [j, w] : g[i]) {
            if (choosenE.find({i, j}) != choosenE.end() || choosenE.find({j, i}) != choosenE.end()) {
                w = 0;
            }
            if (d[i] + w < d[j]) {
                s.erase({d[j], j});
                d[j] = d[i] + w;
                last[j] = i;
                s.insert({d[j], j});
            }
        }
    }
    return d;
}

vector<long long> dijkstraCnt(int start, vector<vector<pair<int, int>>>& g) {
    int n = g.size();
    vector<long long> d(n, numeric_limits<long long>::max()), cnt(n, 0);
    last.assign(n, -1);
    d[start] = 0;
    cnt[start] = 1;
    set<pair<long long, int>> s; // {d[i], i}
    s.insert({0, start});
    while (!s.empty()) {
        int i = s.begin()->second;
        s.erase(s.begin());
        for (auto [j, w] : g[i]) {
            if (d[i] + w < d[j]) {
                s.erase({d[j], j});
                d[j] = d[i] + w;
                cnt[j] = cnt[i];
                last[j] = i;
                s.insert({d[j], j});
            } else if (d[i] + w == d[j]) {
                cnt[j] += cnt[i];
            }
        }
    }
    return cnt;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    cin >> n >> m;
    int s, t;
    cin >> s >> t;
    --s, --t;
    int u, v;
    cin >> u >> v;
    --u, --v;
    vector<vector<pair<int, int>>> g(n);
    for (int _m = 0; _m < m; ++_m) {
        int a, b, w;
        cin >> a >> b >> w;
        --a, --b;
        g[a].push_back({b, w});
        g[b].push_back({a, w});
    }
    if (s == u) {
        long long minDistST = dijkstra(s, g)[t];
        auto dT = dijkstra(t, g), dV = dijkstra(v, g), dS = dijkstra(s, g);
        long long res = numeric_limits<long long>::max();
        for (int i = 0; i < n; ++i) {
            if (dS[i] + dT[i] == minDistST) {
                res = min(res, dV[i]);
            }
        }
        cout << res << '\n';
        return 0;
    }
    if (dijkstraCnt(s, g)[t] == 1) {
        dijkstra(s, g);
        while (t >= 0) {
            choosenE.insert({last[t], t});
            t = last[t];
        }
        auto d = dijkstra2(u, g);
        cout << d[v] << '\n';
        return 0;
    }

    long long minDistST = dijkstra(s, g)[t];
    auto dT = dijkstra(t, g), dV = dijkstra(v, g), dS = dijkstra(s, g), dU = dijkstra(u, g);
    long long res = dU[v];
    for (int i = 0; i < n; ++i) {
        auto di = dijkstra(i, g);
        for (int j = 0; j < n; ++j) {
            if (min(dS[i] + dT[j], dS[j] + dT[i]) + di[j] == minDistST) {
                res = min(res, min(dU[i] + dV[j], dU[j] + dV[i]));
            }
        }
    }
    cout << res << '\n';
    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'std::vector<long long int> dijkstra(int, std::vector<std::vector<std::pair<int, int> > >&)':
commuter_pass.cpp:19:19: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   19 |         for (auto [j, w] : g[i]) {
      |                   ^
commuter_pass.cpp: In function 'std::vector<long long int> dijkstra2(int, std::vector<std::vector<std::pair<int, int> > >&)':
commuter_pass.cpp:41:19: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   41 |         for (auto [j, w] : g[i]) {
      |                   ^
commuter_pass.cpp: In function 'std::vector<long long int> dijkstraCnt(int, std::vector<std::vector<std::pair<int, int> > >&)':
commuter_pass.cpp:67:19: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   67 |         for (auto [j, w] : g[i]) {
      |                   ^

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 45