Submission #651125

#TimeUsernameProblemLanguageResultExecution timeMemory
651125Clan328Connecting Supertrees (IOI20_supertrees)C++17
100 / 100
211 ms24264 KiB
#include "supertrees.h"
#include <vector>
#include <bits/stdc++.h>
 
using namespace std;
 
vector<int> m_link, sz;
 
int m_find(int x) {
	if (m_link[x] != x) m_link[x] = m_find(m_link[x]);
	return m_link[x];
}
 
bool same(int a, int b) {
	return m_find(a) == m_find(b);
}
 
void unite(int a, int b) {
	if (a > b) swap(a, b);
	int x = m_find(b), y = m_find(a);
	if (same(x, y)) return;
	sz[y] += sz[x];
	m_link[x] = y;
}
 
int construct(vector<vector<int>> p) {
	int n = p.size();
	vector<vector<int>> answer(n, vector<int>(n));
 
	m_link = vector<int>(n);
	sz = vector<int>(n, 1);
	iota(m_link.begin(), m_link.end(), 0);
 
	bool res = true;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (i == j) res &= p[i][j] == 1;
			else if (p[i][j] == 1) unite(i, j);
			else if (p[i][j] == 3) res = false;
		}
	}
 
	for (int i = 0; i < n; i++) {
		int par = m_find(i);
		if (par != i) {
			answer[par][i] = 1;
			answer[i][par] = 1;
 
			for (int j = 0; j < n; j++) {
				res &= p[i][j] == p[par][j];
			}
		}
	}
 
	vector<set<int>> newNodes(n);
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (i == j) continue;
			if (p[i][j] == 2) {
				int p1 = m_find(i), p2 = m_find(j);
				unite(p1, p2);
				newNodes[m_find(p1)].insert(p1);
				newNodes[m_find(p2)].insert(p2);
			}
		}
	}
 
	for (int i = 0; i < n; i++) {
		if (newNodes[i].size() == 0) continue;
		res &= newNodes[i].size() > 2;
 
		for (auto it = newNodes[i].begin(); it != newNodes[i].end(); it++) {
			auto nxt = it;
			nxt++;
			
			if (nxt == newNodes[i].end()) {
				nxt = newNodes[i].begin();
			}
			answer[*it][*nxt] = 1;
			answer[*nxt][*it] = 1;
		}
	}
 
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (i == j) continue;
			res &= ((p[i][j] > 0) == same(i, j));
		}
	}
 
	if (res) {
		build(answer);
		return 1;
	} else return 0;
}
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