Language: C++

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

#define fs first
#define sc second
#define pb emplace_back
#define mp make_pair
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()

const int32_t inf = 1001001001;
const int64_t infll = 1001001001001001001ll;
const int dx[] = {0, -1, 1, 0, -1, 1, -1, 1}, dy[] = {-1, 0, 0, 1, -1, -1, 1, 1};

template <typename T> using vector2d = vector<vector<T>>;

// clang-format off
template <typename T> void sort(vector<T> &v) { sort(all(v)); }
// ostream &operator<<(ostream &os, __int128_t value) { if (ostream::sentry(os)) { __uint128_t tmp = value < 0 ? -value : value; char buffer[64]; char *d = end(buffer); do { --d; *d = "0123456789"[tmp % 10]; tmp /= 10; } while (tmp != 0); if (value < 0) { --d; *d = '-'; } int len = end(buffer) - d; if (os.rdbuf()->sputn(d, len) != len) { os.setstate(ios_base::badbit); }} return os; }
// istream &operator>>(istream &is, __int128_t &value) { string in; is >> in; value = 0; for (const char &c : in) { if ('0' <= c && c <= '9') value = 10 * value + (c - '0'); } if (in[0] == '-') value *= -1; return is; }
// ostream &operator<<(ostream &os, __uint128_t value) { if (ostream::sentry(os)) { char buffer[64]; char *d = end(buffer); do { --d; *d = "0123456789"[value % 10]; value /= 10; } while (value != 0); int len = end(buffer) - d; if (os.rdbuf()->sputn(d, len) != len) { os.setstate(ios_base::badbit); }} return os; }
// istream &operator>>(istream &is, __uint128_t &value) { string in; is >> in; value = 0; for (const char &c : in) { if ('0' <= c && c <= '9') value = 10 * value + (c - '0'); } return is; }
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) { os << v[0]; for (int i = 1; i < v.size(); ++i) os << " " << v[i]; return os; }
template <typename T> istream &operator>>(istream &is, vector<T> &v) { for (T &in : v) is >> in; return is; }
template <typename T1, typename T2> ostream &operator<<(ostream &os, pair<T1, T2> p) { os << p.fs << " " << p.sc; return os; }
template <typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.fs >> p.sc; return is; }

struct IoSetup { IoSetup(){ cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10); cerr << fixed << setprecision(10); } } iosetup;

inline int64_t in() { int64_t x = 0; cin >> x; return x; }
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }
// clang-format on

// 0123456

int n = in();
k = in();
vector2d<int> a(2 * k + 1, vector<int>(2 * k + 1));

int sum(int y, int x, int Y, int X) {
  return a[Y][X] + a[y][x] - a[Y][x] - a[y][X];
}

int query(int y, int x) {
  return sum(0, 0, y, x) + sum(y, x, y + k, x + k) + sum(y + k, x + k, 2 * k, 2 * k) + sum(y + k, 0, 2 * k, x) +
         sum(0, x + k, y, 2 * k);
}

signed main(int argc, char *argv[]) {
  for (int i = 0; i < n; ++i) {
    int x, y;
    char c;
    cin >> x >> y >> c;

    if (c == 'B') x += k;

    x %= 2 * k;
    y %= 2 * k;

    a[y + 1][x + 1]++;
  }

  for (int i = 1; i <= 2 * k; ++i) {
    for (int j = 1; j <= 2 * k; ++j) {
      a[i][j] += a[i - 1][j] + a[i][j - 1] - a[i - 1][j - 1];
    }
  }

  int ans = 0;
  for (int i = 0; i <= k; ++i) {
    for (int j = 0; j <= k; ++j) {
      chmax(ans, max(n - query(i, j), query(i, j)));
    }
  }

  cout << ans << endl;
}


Compiler output:
a.cc:38:1: error: 'k' does not name a type
   38 | k = in();
      | ^
a.cc:39:21: error: 'k' was not declared in this scope
   39 | vector2d<int> a(2 * k + 1, vector<int>(2 * k + 1));
      |                     ^
a.cc:39:44: error: 'k' was not declared in this scope
   39 | vector2d<int> a(2 * k + 1, vector<int>(2 * k + 1));
      |                                            ^
a.cc: In function 'int query(int, int)':
a.cc:46:42: error: 'k' was not declared in this scope
   46 |   return sum(0, 0, y, x) + sum(y, x, y + k, x + k) + sum(y + k, x + k, 2 * k, 2 * k) + sum(y + k, 0, 2 * k, x) +
      |                                          ^
a.cc: In function 'int main(int, char**)':
a.cc:56:24: error: 'k' was not declared in this scope
   56 |     if (c == 'B') x += k;
      |                        ^
a.cc:58:14: error: 'k' was not declared in this scope
   58 |     x %= 2 * k;
      |              ^
a.cc:64:28: error: 'k' was not declared in this scope
   64 |   for (int i = 1; i <= 2 * k; ++i) {
      |                            ^
a.cc:71:24: error: 'k' was not declared in this scope
   71 |   for (int i = 0; i <= k; ++i) {
      |                        ^