Submission #860475

#	Time	Username	Problem	Language	Result	Execution time	Memory
860475		The_Samurai	Railway (BOI17_railway)	C++17	0 / 100	89 ms	68908 KiB

railway

#include "bits/stdc++.h"

using namespace std;
using ll = long long;
const int lg = 17;

int main() {
    cin.tie(0)->sync_with_stdio(false);
#ifdef sunnatov
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    int n, m, k;
    cin >> n >> m >> k;
    vector<vector<int>> g(n + 1), jump(n + 1, vector<int>(lg));
    map<pair<int, int>, int> mp;
    for (int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        g[u].emplace_back(v);
        g[v].emplace_back(u);
        mp[make_pair(min(u, v), max(u, v))] = i;
    }
    vector<int> tin(n + 1), tout(n + 1), par(n + 1);
    int z = 0;
    auto dfs = [&](auto &dfs, int u) -> void {
        if (par[u] != 0) {
            for (int i = 1; i < lg; i++) {
                jump[i][u] = jump[i - 1][jump[i - 1][u]];
                if (jump[i][u] == 0) break;
            }
        }
        tin[u] = z++;
        for (int v: g[u]) {
            if (jump[0][u] == v) continue;
            jump[0][v] = u;
            par[v] = u;
            dfs(dfs, v);
        }
        tout[u] = z++;
    };
    auto isAnc = [&](int u, int v) {
        return tin[u] <= tin[v] and tout[v] <= tout[u];
    };
    auto lca = [&](int u, int v) {
        if (isAnc(u, v)) return u;
        if (isAnc(v, u)) return v;
        for (int i = lg - 1; i >= 0; i--) {
            if (jump[i][u] == 0 or isAnc(jump[i][u], v)) continue;
            u = jump[i][u];
        }
        return jump[0][u];
    };
    dfs(dfs, 1);
    vector<int> cnt(n + 1);
    while (m--) {
        int ln;
        cin >> ln;
        vector<int> a(ln);
        for (int &x: a) cin >> x;
        if (ln == 1) continue;
        int anc = a[0];
        for (int i = 1; i < ln; i++) anc = lca(anc, a[i]);
        cnt[anc]++;
        for (int i = 0; i < ln; i++) {
            bool ok = true;
            for (int j = 0; j < ln; j++) {
                if (i != j) ok &= !isAnc(a[i], a[j]);
            }
            if (ok) cnt[a[i]]--;
        }
    }
//    for (int i = 1; i <= n; i++) cout << cnt[i] << ' ';
//    cout << endl;
    vector<int> ans;
    auto dfs2 = [&](auto &dfs2, int u) -> void {
        for (int v: g[u]) {
            if (par[u] == v) continue;
            dfs2(dfs2, v);
            cnt[v] += cnt[u];
        }
//        cout << u << ' ' << cnt[par[u]] << '\n';
        if (cnt[par[u]] >= k) ans.emplace_back(mp[make_pair(min(u, par[u]), max(u, par[u]))]);
    };
    dfs2(dfs2, 1);
    sort(ans.begin(), ans.end());
    cout << ans.size() << '\n';
    for (int x: ans) cout << x << ' ';
}

• Subtask 1: 0 / 8
• Subtask 2: 0 / 15
• Subtask 3: 0 / 7
• Subtask 4: 0 / 29
• Subtask 5: 0 / 16
• Subtask 6: 0 / 25