Submission #909954

#	Time	Username	Problem	Language	Result	Execution time	Memory
909954		Pekiban	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	500 ms	21084 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

const int mxN = 1e5+2;
const long long inf = 1e18;
vector<pair<int, int>> g[mxN];
vector<long long> dists(mxN), distu(mxN), distv(mxN), mn(mxN), dist(mxN);
bool visited[mxN];
void dijkstra(int s, vector<long long> &dist) {
    fill(visited, visited+mxN, 0);
    fill(dist.begin(), dist.end(), inf);
    dist[s] = 0;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<>> pq;
    pq.push({0, s});
    while (!pq.empty()) {
        auto [x, u] = pq.top();
        pq.pop();
        if (visited[u]) continue;
        visited[u] = 1;
        for (auto [v, w] : g[u]) {
            if (dist[v] > x + w) {
                dist[v] = x + w;
                pq.push({dist[v], v});
            }
        }
    }
}
int n, m;
long long f(int S, int T, int U, int V) {
    dijkstra(S, dists); dijkstra(U, distu); dijkstra(V, distv);
    fill(visited, visited+mxN, 0);
    fill(mn.begin(), mn.end(), inf);
    fill(dist.begin(), dist.end(), inf);
    dist[T] = 0;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<>> pq;
    pq.push({0, T});
    while (!pq.empty()) {
        auto [x, u] = pq.top();
        pq.pop();
        if (visited[u]) continue;
        visited[u] = 1;
        mn[u] = distv[u];
        for (auto [v, w] : g[u]) {
            if (x == dist[v] + w) {
                mn[u] = min(mn[v], mn[u]);
            }
            if (dist[v] > w + x) {
                dist[v] = w + x;
                pq.push({dist[v], v});
            }
        }
    }
    long long ans = distu[V], anss = inf;
    for (int i = 1; i <= n; ++i) {
        if (dists[i] + dist[i] == dists[T]) ans = min(ans, distu[i] + mn[i]);
    }
    return ans;
}
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    int S, T, U, V;
    cin >> S >> T >> U >> V;
    for (int i = 0; i < m; ++i) {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].push_back({v, w}), g[v].push_back({u, w});
    }
    cout << min(f(S, T, U, V), f(T, S, U, V)) << '\n';
}

Compilation message (stderr)

commuter_pass.cpp: In function 'long long int f(int, int, int, int)':
commuter_pass.cpp:54:31: warning: unused variable 'anss' [-Wunused-variable]
   54 |     long long ans = distu[V], anss = inf;
      |                               ^~~~

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