Ruudukko

#include <climits>
#include <cstdint>
#include <iostream>
#include <map>
#include <vector>

using namespace std;

int main() {
    cin.sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    vector<bool> kaannot((n + 1) * (n + 1));

    auto kaanna = [&](int i, int j) {
        int p = (n + 1) * i + j;
        kaannot[p] = !kaannot[p];
    };

    for(int i = 0; i < m; ++i) {
        int i1, j1, i2, j2;
        cin >> i1 >> j1 >> i2 >> j2;
        --i1;
        --j1;
        kaanna(i1, j1);
        kaanna(i1, j2);
        kaanna(i2, j1);
        kaanna(i2, j2);
    }

    vector<bool> tulos(n * n);
    for(int i = 0; i < n; ++i) {
        bool riviArvo = false;
        for(int j = 0; j < n; ++j) {
            if(kaannot[(n + 1) * i + j]) {
                riviArvo = !riviArvo;
            }
            bool arvo = riviArvo;
            if(i > 0 && tulos[n * (i - 1) + j]) {
                arvo = !arvo;
            }
            tulos[n * i + j] = arvo;
        }
    }

    for(int i = 0; i < n; ++i) {
        for(int j = 0; j < n; ++j) {
            cout << (tulos[n * i + j] ? '#' : '.');
        }
        cout << "\n";
    }

    return 0;
}

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: ACCEPTED