Submission #300354

#	Time	Username	Problem	Language	Result	Execution time	Memory
300354		Elegia	Connecting Supertrees (IOI20_supertrees)	C++17	100 / 100	272 ms	22264 KiB

supertrees

#include "supertrees.h"
#include <functional>
#include <vector>
#include <iostream>

using namespace std;

int construct(vector<vector<int>> p) {
	int n = p.size();
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			if (p[i][j] == 3) return 0;
	vector<vector<int>> answer(n, vector<int>(n));
	vector<int> vis(n, -1);
	int cur = 0, mask = 0;
	function<void(int)> dfs = [&](int u) {
		vis[u] = cur;
		for (int v = 0; v < n; ++v)
			if (vis[v] == -1 && ((mask >> p[u][v]) & 1))
				dfs(v);
	};
	mask = 6;
	for (int i = 0; i < n; ++i)
		if (vis[i] == -1) {
			cur = i;
			dfs(i);
		}
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			if (vis[i] == vis[j] && !p[i][j])
				return 0;
	mask = 2;
	auto vis2 = vis;
	vis.assign(n, -1);
	for (int i = 0; i < n; ++i)
		if (vis[i] == -1) {
			cur = i;
			dfs(i);
		}
	for (int i = 0; i < n; ++i)
		for (int j = 0; j < n; ++j)
			if (vis[i] == vis[j] && p[i][j] == 2)
				return 0;
	vector<int> cand(n, -1);
	vector<vector<int>> cycs(n);
	for (int i = 0; i < n; ++i) {
		if (cand[vis[i]] == -1) {
			cand[vis[i]] = i;
			cycs[vis2[i]].push_back(i);
		} else {
			answer[cand[vis[i]]][i] = answer[i][cand[vis[i]]] = 1;
		}
	}
	for (auto cyc : cycs) {
		if (cyc.size() > 1) {
			if (cyc.size() < 3) return 0;
			answer[cyc[0]][cyc.back()] = answer[cyc.back()][cyc[0]] = 1;
			for (int i = 1; i < cyc.size(); ++i)
				answer[cyc[i - 1]][cyc[i]] = answer[cyc[i]][cyc[i - 1]] = 1;
		}
	}
	build(answer);
	return 1;
}

Compilation message (stderr)

supertrees.cpp: In function 'int construct(std::vector<std::vector<int> >)':
supertrees.cpp:58:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |    for (int i = 1; i < cyc.size(); ++i)
      |                    ~~^~~~~~~~~~~~

• Subtask 1: 11 / 11
• Subtask 2: 10 / 10
• Subtask 3: 19 / 19
• Subtask 4: 35 / 35
• Subtask 5: 21 / 21
• Subtask 6: 4 / 4