Ruudukko

#include <cstdint>
#include <string>
#include <iostream>
#include <vector>

int main()
{
	int n, m;
	std::cin >> n >> m;
	std::cin.ignore();

	int bits = n * n;
	std::vector<uint64_t> ruudukko(bits / 64 + 1);
	int y1, x1, y2, x2;
	for (int i = 0; i < m; ++i)
	{
		std::cin >> y1 >> x1 >> y2 >> x2;
		y1--; x1--; y2--; // x2--;

		for (int y = y1; y <= y2; ++y)
		{
			int index1 = y * n + x1;
			int index2 = y * n + x2;

			auto& element1 = ruudukko[index1 / 64];
			auto& element2 = ruudukko[index2 / 64];

			if (&element1 == &element2)
				element1 ^= (1ULL << (63 - index1 % 64)) | (1ULL << (63 - index2 % 64));
			else
			{
				element1 ^= (1ULL << (63 - index1 % 64));
				element2 ^= (1ULL << (63 - index2 % 64));
			}
		}
	}

	std::string printtaus;
	char merkki = '.';
	for (int i = 0; i < n * n; ++i)
	{
		const auto& element = ruudukko[i / 64];
		int bit = element >> (63 - i % 64) & 1;
		if (bit == 1)
			merkki = merkki == '.' ? '#' : '.';
		printtaus += merkki;
	}

	for (int i = 1; i < n; ++i)
		printtaus.insert(i * n + i - 1, 1, '\n');

	std::cout << printtaus << std::endl;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 2, 3

Verdict: ACCEPTED

Test 3

Group: 2, 3

Verdict: ACCEPTED

Test 4

Group: 3

Verdict: ACCEPTED

Test 5

Group: 3

Verdict: TIME LIMIT EXCEEDED