Submission #768561

#	Time	Username	Problem	Language	Result	Execution time	Memory
768561		flappybird	Pastiri (COI20_pastiri)	C++17	31 / 100	1090 ms	181196 KiB

pastiri

#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2,fma")
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
#define MAX 500101
#define MAXS 25
#define INF 1000000000000000001
#define bb ' '
#define ln '\n'
#define Ln '\n'
vector<int> adj[MAX];
int dis[MAX];
int sheep[MAX];
vector<int> v;
int vis[MAX];
int dep[MAX];
int prt[MAX];
int sp[MAX][MAXS];
int N, K;

namespace centroid {
	int cp[MAX];
	int cd[MAX];
	int num[MAX];
	int vis[MAX];
	int mx[MAX];
	int dis[MAXS][MAX];
	void make_num(int x, int p = 0) {
		num[x] = 1;
		for (auto v : adj[x]) if (v != p) {
			if (vis[v]) continue;
			make_num(v, x);
			num[x] += num[v];
		}
	}
	void make_dis(int x, int c, int p = 0) {
		for (auto v : adj[x]) {
			if (vis[v]) continue;
			if (v == p) continue;
			dis[c][v] = dis[c][x] + 1;
			make_dis(v, c, x);
		}
	}
	void make_tree(int x, int p = 0, int d = 0) {
		assert(d < MAXS);
		make_num(x);
		int c = x;
		int n = num[x];
		while (1) {
			bool changed = false;
			for (auto v : adj[c]) {
				if (num[v] > num[c]) continue;
				if (vis[v]) continue;
				if (num[v] > n / 2) {
					c = v;
					changed = true;
					break;
				}
			}
			if (!changed) break;
		}
		make_dis(c, d);
		vis[c] = 1;
		cp[c] = p;
		cd[c] = d;
		for (auto v : adj[c]) {
			if (vis[v]) continue;
			make_tree(v, c, d + 1);
		}
	}
	inline void upd(int i, int d) {
		int v = i;
		while (v) {
			mx[v] = max(mx[v], d - dis[cd[v]][i]);
			v = cp[v];
		}
	}
	inline int chk(int i) {
		int v = i;
		while (v) {
			if (dis[cd[v]][i] <= mx[v]) return true;
			v = cp[v];
		}
		return false;
	}
	void init() {
		make_tree(1);
		for (int i = 1; i <= N; i++) mx[i] = -1;
	}
}

void dfs(int x, int p = 0) {
	if (sheep[x]) dis[x] = 0;
	else dis[x] = 10101010;
	prt[x] = p;
	sp[x][0] = p;
	int i;
	for (i = 1; i < MAXS; i++) sp[x][i] = sp[sp[x][i - 1]][i - 1];
	for (auto v : adj[x]) {
		if (v == p) continue;
		dep[v] = dep[x] + 1;
		dfs(v, x);
		dis[x] = min(dis[x], dis[v] + 1);
	}
}
void down(int x, int p = 0) {
	for (auto v : adj[x]) if (v != p) {
		dis[v] = min(dis[v], dis[x] + 1);
		down(v, x);
	}
}
void chk(int x, int d, int p = 0) {
	sheep[x] = 0;
	if (!d) return;
	for (auto v : adj[x]) if (v != p) chk(v, d - 1, x);
}
signed main() {
	ios::sync_with_stdio(false), cin.tie(0);
	cin >> N >> K;
	int i, a, b;
	for (i = 1; i < N; i++) {
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	vector<int> sv;
	for (i = 1; i <= K; i++) {
		cin >> a;
		sv.push_back(a);
		sheep[a] = 1;
	}
	dfs(1);
	down(1);
	sort(sv.begin(), sv.end(), [&](int a, int b) {return dep[a] > dep[b]; });
	int cnt = 0;
	vector<int> ans;
	centroid::init();
	for (auto x : sv) {
		if (centroid::chk(x)) continue;
		cnt++;
		int v = x;
		for (i = MAXS - 1; i >= 0; i--) {
			int p = sp[v][i];
			if (!p) continue;
			if (dis[p] >= dep[x] - dep[p]) v = p;
		}
		ans.push_back(v);
		centroid::upd(v, dis[v]);
	}
	cout << ans.size() << ln;
	for (auto v : ans) cout << v << bb;
}

• Subtask 1: 8 / 8
• Subtask 2: 0 / 18
• Subtask 3: 23 / 23
• Subtask 4: 0 / 51