Ruudukko

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

bool t[2001][2001];
bool current[2001];

void ch_bit(int y, int x){
    t[y][x] = 1 - t[y][x];
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    for (int i=1; i<=m; ++i){
        int y1, x1, y2, x2;
        cin >> y1 >> x1 >> y2 >> x2;
        ch_bit(y1, x1);
        ch_bit(y1, x2+1);
        ch_bit(y2+1, x1);
        ch_bit(y2+1, x2+1);
    }
    for (int i=1; i<=n; ++i){
        bool a = false;
        for (int j=1; j<=n; ++j){
            if (t[i][j]) current[j] = 1 - current[j];
            if (current[j]) a = 1 - a;
            if (a) cout << "#";
            else cout << ".";
        }
        cout << "\n";
    }
    
}

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