Submission #1221596

#	Time	Username	Problem	Language	Result	Execution time	Memory
1221596		madamadam3	Commuter Pass (JOI18_commuter_pass)	C++20	24 / 100	2096 ms	117856 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;

#define int long long int

using pi = pair<int, int>;
using vb = vector<bool>;
using vi = vector<int>;
using vvi = vector<vi>;
using vpi = vector<pi>;
using vvpi = vector<vpi>;

struct DSU {
    int n; vector<int> par, siz;

    DSU(int N) {
        n = N;
        par.resize(n); iota(par.begin(), par.end(), 0);
        siz.assign(n, 1);
    }

    int find(int v) {
        if (v == par[v]) return v;
        return par[v] = find(par[v]);
    }

    void unite(int a, int b) {
        a = find(a); b = find(b);
        if (a != b) {
            if (siz[a] < siz[b]) swap(a, b);
            par[b] = a;

            siz[a] += siz[b];
        }
    }
};

const int MAXN = 100'001, MAXM = 200'001;
const int INF = numeric_limits<int>::max();
int n, m, X[MAXM], Y[MAXM], C[MAXM];
int S, T, U, V;
vi adj[MAXN], mst_adj[MAXN];

void dijkstra(int u, vi &dist, vi &par) {
    dist.assign(n+1, INF);
    par.assign(n+1, -1);

    dist[u] = 0; par[u] = -1;
    priority_queue<pi, vector<pi>, greater<pi>> q;
    q.push({0, u});

    while (!q.empty()) {
        auto cur = q.top();
        q.pop();

        int cu = cur.second, cdist = cur.first;

        for (auto &el : adj[cu]) {
            int cv = X[el] == cu ? Y[el] : X[el];
            int vdist = C[el];

            if(dist[cu] + vdist < dist[cv]) {
                par[cv] = cu;
                dist[cv] = dist[cu] + vdist;
                q.push({dist[cu] + vdist, cv});
            }
        }
    }
}
signed main() {
    cin >> n >> m;
    cin >> S >> T >> U >> V;

    for (int i = 1; i <= m; i++) {
        cin >> X[i] >> Y[i] >> C[i];
        adj[X[i]].push_back(i);
        adj[Y[i]].push_back(i);
    }

    vi edges(m+1); iota(edges.begin(), edges.end(), 0);
    sort(edges.begin(), edges.end(), [&](int a, int b) {return C[a] < C[b];});
    auto dsu = DSU(n+1);
    for (auto &edge : edges) {
        if (dsu.find(X[edge]) == dsu.find(Y[edge])) continue;
        dsu.unite(X[edge], Y[edge]);
        mst_adj[X[edge]].push_back(edge);
        mst_adj[Y[edge]].push_back(edge);
    }

    vvi dist(n+1, vi());
    vvi parents(n+1, vi());

    for (int i = 1; i <= n; i++) {
        dijkstra(i, dist[i], parents[i]);
    }

    int stdist = dist[S][T];
    vi on_sp; for (int i = 1; i <= n; i++) {
        if (dist[i][S] + dist[i][T] != stdist) continue;
        on_sp.push_back(i);
    }

    int best = dist[U][V];
    for (auto &x : on_sp) {
        for (auto &y : on_sp) {
            if (dist[S][x] + dist[T][y]+ dist[x][y] != stdist) continue;
            best = min(best, dist[U][x] + dist[V][y]);
        }

        for (auto &y : on_sp) {
            if (dist[T][x] + dist[S][y]+ dist[x][y] != stdist) continue;
            best = min(best, dist[U][x] + dist[V][y]);
        }
    }

    cout << best;
    return 0;
}

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