Ruudukko

#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int n, m;

#define N 2003

int fen[N][N];

void add(int t, int k, int x) {
  for (; k <= N; fen[t][k] += x, k += k & -k);
}

int upto(int t, int k) {
  int s = 0;
  for (; k >= 1; s += fen[t][k], k -= k & -k);
  return s;
}

int main() {
  ios_base::sync_with_stdio(0); cin.tie(0);
  cin>>n>>m;

  for (int qi = 0; qi < m; qi++) {
    int y1, x1, y2, x2;
    cin>>y1>>x1>>y2>>x2;
    add(x1, y1, 1);
    add(x1, y2+1, -1);
    add(x2+1, y1, -1);
    add(x2+1, y2+1, 1);
  }

  for (int y = 1; y <= n; y++) {
    int rowsum = 0;
    for (int x = 1; x <= n; x++) {
      rowsum += upto(x, y);
      cout << ((rowsum & 1) ? '#' : '.');
    }
    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