Submission #260450

#	Time	Username	Problem	Language	Result	Execution time	Memory
260450		dolphingarlic	Railway (BOI17_railway)	C++14	100 / 100	315 ms	23536 KiB

railway

#include <bits/stdc++.h>
typedef long long ll;
using namespace std;

int n, m, k;
vector<pair<int, int>> graph[100001];
int tin[100001], tout[100001], timer = 0, anc[100001][20], p_edge[100001];
int chosen[50001];
int bit1[100001], bit2[100001];

void dfs(int node = 1, int parent = 0) {
	tin[node] = ++timer;
	for (int i = 1; i < 20; i++) anc[node][i] = anc[anc[node][i - 1]][i - 1];
	for (pair<int, int> i : graph[node]) if (i.first != parent) {
		anc[i.first][0] = node;
		p_edge[i.first] = i.second;
		dfs(i.first, node);
	}
	tout[node] = timer;
}

bool is_ancestor(int a, int b) {
	return (tin[a] <= tin[b] && tout[a] >= tout[b]);
}

int lca(int a, int b) {
	if (is_ancestor(a, b)) return a;
	for (int i = 19; ~i; i--) {
		if (anc[a][i] && !is_ancestor(anc[a][i], b)) a = anc[a][i];
	}
	return anc[a][0];
}

void update(int bit[100001], int pos, int val) {
	for (; pos <= n; pos += pos & (-pos)) bit[pos] += val;
}

int query(int bit[100001], int a, int b) {
	int ans = 0;
	for (; b; b -= b & (-b)) ans += bit[b];
	for (a--; a; a -= a & (-a)) ans -= bit[a];
	return ans;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> m >> k;
	for (int i = 1; i < n; i++) {
		int a, b;
		cin >> a >> b;
		graph[a].push_back({b, i});
		graph[b].push_back({a, i});
	}

	dfs();

	while (m--) {
		int s, l;
		cin >> s;
		for (int i = 0; i < s; i++) {
			cin >> chosen[i];
			if (!i) l = chosen[i];
			else l = lca(l, chosen[i]);
		}
		for (int i = 0; i < s; i++) {
			int curr = chosen[i];
			if (curr == l) continue;
			for (int j = 19; ~j; j--) {
				int nxt = anc[curr][j];
				if (nxt && !is_ancestor(nxt, l) && !query(bit2, tin[nxt], tout[nxt])) {
					update(bit1, tin[curr], 1);
					update(bit2, tin[curr], 1);
					update(bit1, tin[nxt], -1);
					update(bit2, tin[nxt], -1);
					curr = nxt;
				}
			}
			update(bit1, tin[curr], 1);
			update(bit2, tin[curr], 1);
			update(bit1, tin[anc[curr][0]], -1);
			update(bit2, tin[anc[curr][0]], -1);
		}
		for (int i = 0; i < s; i++) {
			int curr = chosen[i];
			if (curr == l) continue;
			for (int j = 19; ~j; j--) {
				int nxt = anc[curr][j];
				if (nxt && !is_ancestor(nxt, l) && query(bit2, tin[nxt], tout[nxt])) {
					update(bit2, tin[curr], -1);
					update(bit2, tin[nxt], 1);
					curr = nxt;
				}
			}
			update(bit2, tin[curr], -1);
			update(bit2, tin[anc[curr][0]], 1);
		}
	}

	vector<int> ans;
	for (int i = 2; i <= n; i++) if (query(bit1, tin[i], tout[i]) >= k) {
		ans.push_back(p_edge[i]);
	}
	sort(ans.begin(), ans.end());
	cout << ans.size() << '\n';
	for (int i : ans) cout << i << ' ';
	return 0;
}

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