Submission #1264029

#	Time	Username	Problem	Language	Result	Execution time	Memory
1264029		mingga	Railway (BOI17_railway)	C++20	36 / 100	58 ms	24124 KiB

railway

// Author: caption_mingle
#include "bits/stdc++.h"

using namespace std;

#define ln "\n"
#define pb push_back
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ll long long
const int mod = 1e9 + 7;
const int inf = 2e9;
const int N = 1e5 + 7;
int n, m, k, h[N], up[N][20];
int timer, in[N], out[N], cnt[N], id[N];
pair<int, int> edge[N];
vector<int> g[N];

void dfs(int u, int p) {
	in[u] = ++timer;
	for(int i = 1; i <= 16; i++) up[u][i] = up[up[u][i - 1]][i - 1];
	for(int v : g[u]) {
		if(v == p) continue;
		h[v] = h[u] + 1;
		up[v][0] = u;		
		dfs(v, u);
	}
	out[u] = timer;
}

int lca(int u, int v) {
	if(h[u] < h[v]) swap(u, v);
	int k = h[u] - h[v];
	for(int i = 0; (1 << i) <= k; i++) {
		if(k >> i & 1) u = up[u][i];
	}
	if(u == v) return u;
	for(int i = 16; i >= 0; i--) {
		if(up[u][i] != up[v][i]) {
			u = up[u][i];
			v = up[v][i];
		}
	}
	return up[u][0];
}

bool inside(int u, int v) {
	return in[u] <= in[v] and out[v] <= out[u];
}

signed main() {
	cin.tie(0) -> sync_with_stdio(0);
	#define task ""
	if(fopen(task ".INP", "r")) {
		freopen(task ".INP", "r", stdin);
		freopen(task ".OUT", "w", stdout);
	}
	cin >> n >> m >> k;
	for(int i = 1; i < n; i++) {
		int u, v; cin >> u >> v;
		g[u].pb(v);
		g[v].pb(u);
		edge[i] = {u, v};
	}
	dfs(1, 0);
	for(int i = 1; i <= m; i++) {
		int sz; cin >> sz;
		vector<int> vec;
		for(int j = 1; j <= sz; j++) {
			int x; cin >> x;
			vec.pb(x);
		}
		for(int j = 1; j < sz; j++) {
			vec.pb(lca(vec[j], vec[j - 1]));
		}
		sort(all(vec), [&](int x, int y) {
			return in[x] < in[y];
		});
		vec.erase(unique(all(vec)), vec.end());
		vector<int> st;
		for(int u : vec) {
			while(sz(st) and !inside(st.back(), u)) st.pop_back();
			if(sz(st)) {
				cnt[st.back()]--;
				// cerr << st.back() << ' ' << u << ln;
				cnt[u]++;
			}
			st.pb(u);
		}
	}
	for(int i = 1; i < n; i++) {
		auto& [u, v] = edge[i];
		if(h[v] < h[u]) swap(u, v);
		// cerr << "EDGE " << u << ' ' << v << ' ' << i << ln;
		id[v] = i;
	}
	vector<int> vec;
	for(int i = 1; i <= n; i++) vec.pb(i);
	sort(all(vec), [&](int x, int y) {
		return h[x] > h[y];
	});
	vector<int> ans;
	for(int x : vec) {
		cnt[up[x][0]] += cnt[x];
		// cerr << x << ' ' << cnt[x] << ln;
		if(cnt[x] >= k) ans.pb(id[x]);
	}
	cout << sz(ans) << ln;
	sort(all(ans));
	for(int x : ans) cout << x << ' ';
    cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC;
}

Compilation message (stderr)

railway.cpp: In function 'int main()':
railway.cpp:57:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |                 freopen(task ".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
railway.cpp:58:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   58 |                 freopen(task ".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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