#include <bits/stdc++.h> #define taskname "" using namespace std; using ld = long double; using ull = unsigned long long; using ll = long long; using pii = pair <int, int>; const char el = '\n'; const char sp = ' '; const int maxN = 2e5 + 10; const int LOG = 21; int n, m, k, timer; int st[maxN], en[maxN], sub[maxN], head[maxN], edge_idx[maxN]; int up[maxN][LOG]; vector <pii> adj[maxN]; int bit[maxN]; void update(int x, int v) { for (; x < maxN; x += x & -x) bit[x] += v; } int query(int x) { int res = 0; for (; x > 0; x -= x & -x) res += bit[x]; return res; } void dfs_sz(int u, int p) { sub[u] = 1; up[u][0] = p; for (int i = 1; i < LOG; ++i) up[u][i] = up[up[u][i - 1]][i - 1]; for (int i = 0; i < (int)adj[u].size(); ++i) { if (adj[u][i].first == p) continue; dfs_sz(adj[u][i].first, u); sub[u] += sub[adj[u][i].first]; if (adj[u][0].first == p || sub[adj[u][i].first] > sub[adj[u][0].first]) { swap(adj[u][0], adj[u][i]); } } } void dfs_hld(int u, int p, int h, int weight) { st[u] = ++timer; head[u] = h; edge_idx[u] = weight; for (int i = 0; i < (int)adj[u].size(); ++i) { int v = adj[u][i].first; int w = adj[u][i].second; if (v == p) continue; dfs_hld(v, u, (i == 0 ? h : v), w); } en[u] = timer; } bool is_anc(int u, int v) { return st[u] <= st[v] && en[u] >= en[v]; } int get_lca(int u, int v) { if (is_anc(u, v)) return u; if (is_anc(v, u)) return v; for (int i = LOG - 1; i >= 0; --i) { if (up[u][i] && !is_anc(up[u][i], v)) u = up[u][i]; } return up[u][0]; } void path_upd(int u, int v, int val) { while (head[u] != head[v]) { update(st[head[v]], val); update(st[v] + 1, -val); v = up[head[v]][0]; } update(st[u], val); update(st[v] + 1, -val); } int main () { ios_base::sync_with_stdio(0); cin.tie(0); if (fopen(taskname ".inp", "r")) { freopen(taskname ".inp", "r", stdin); freopen(taskname ".out", "w", stdout); } if (!(cin >> n >> m >> k)) return 0; for (int i = 1; i < n; ++i) { int u, v; cin >> u >> v; adj[u].push_back({v, i}); adj[v].push_back({u, i}); } dfs_sz(1, 0); dfs_hld(1, 0, 1, 0); while (m--) { int num; cin >> num; vector <int> v(num); for (int &x : v) cin >> x; sort(v.begin(), v.end(), [&](int a, int b) { return st[a] < st[b]; }); for (int i = 1; i < num; ++i) v.push_back(get_lca(v[i - 1], v[i])); sort(v.begin(), v.end(), [&](int a, int b) { return st[a] < st[b]; }); v.erase(unique(v.begin(), v.end()), v.end()); for (int i = 1; i < (int)v.size(); ++i) { int l = get_lca(v[i - 1], v[i]); int curr = v[i]; for (int j = LOG - 1; j >= 0; --j) { if (up[curr][j] && !is_anc(up[curr][j], l)) curr = up[curr][j]; } path_upd(curr, v[i], 1); } } vector <int> res; for (int i = 2; i <= n; ++i) { if (query(st[i]) >= k) res.push_back(edge_idx[i]); } sort(res.begin(), res.end()); cout << res.size() << el; for (int x : res) cout << x << sp; cout << el; return 0; }

railway.cpp: In function 'int main()':
railway.cpp:98:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   98 |         freopen(taskname ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:99:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   99 |         freopen(taskname ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~