Submission #1282080

#	Time	Username	Problem	Language	Result	Execution time	Memory
1282080		AksLolCoding	The Ties That Guide Us (CEOI23_incursion)	C++17	100 / 100	174 ms	7524 KiB

incursion

#include <bits/stdc++.h>
using namespace std;
#include "incursion.h"

int n;
vector<int> adj[45010];
vector<int> cen;
int siz[45010];
int par[45010];

void f(int x, int p) {
	bool ok = 1;
	siz[x] = 1;
	for (int y : adj[x]) {
		if (y == p) continue;
		f(y, x);
		siz[x] += siz[y];
		if (siz[y] > n / 2) ok = 0;
	}
	if (n - siz[x] > n / 2) ok = 0;
	if (ok) cen.push_back(x);
}

void g(int x, int p) {
	par[x] = p;
	siz[x] = 1;
	for (int y : adj[x]) {
		if (y == p) continue;
		g(y, x);
		siz[x] += siz[y];
	}
}

void init(vector<pair<int, int>>& F) {
	n = (int)F.size() + 1;
	for (auto [x, y] : F) {
		adj[x].push_back(y);
		adj[y].push_back(x);
	}
	f(1, -1);
	if ((int)cen.size() == 1) cen.push_back(-1);
	assert((int)cen.size() == 2);
	g(cen[0], cen[1]);
	if (cen[1] != -1) g(cen[1], cen[0]);
}

vector<int> mark(vector<pair<int, int>> F, int safe) {
	init(F);
	vector<int> res(n);
	int x = safe;
	while (1) {
		res[x - 1] = 1;
		if (x == cen[0] || x == cen[1]) break;
		x = par[x];
	}
	return res;
}

void locate(vector<pair<int, int>> F, int curr, int t) {
	init(F);
	int x = curr;
	while (t == 0) {
		t = visit(par[x]);
		x = par[x];
	}
	while (1) {
		vector<pair<int, int>> nx;
		for (int y : adj[x]) {
			if (y == par[x]) continue;
			nx.push_back({siz[y], y});
		}
		sort(nx.rbegin(), nx.rend());
		bool ok = 1;
		for (auto [_, y] : nx) {
			if (visit(y)) {
				ok = 0;
				x = y;
				break;
			}
			visit(x);
		}
		if (ok) return;
	}
}

• Subtask 0: 0 / 0
• Subtask 1: 30 / 30
• Subtask 2: 30 / 30
• Subtask 3: 40 / 40