Ruudukko

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

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

	std::vector<char> ruudukko(n * n);

	for (int j = 0; j < m; ++j)
	{
		int a, b, c, d;
		std::cin >> a >> b >> c >> d;
		a--; b--; c--; d--;

		int y = c - a;

		for (int i = 0; i <= y; ++i)
		{
			int r = (a + i) * n;
			ruudukko[r + b] ^= 1;
			ruudukko[r + d + 1] ^= 1;
		}
	}

	std::string printtaus;
	printtaus.reserve(n * n + n);
	char merkki = '.';
	for (int ruutu : ruudukko)
	{
		if ((ruutu & 1) == 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