Problem p02580 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
const int INF = 1e9;
const int MOD = 1e9 + 7;
const long long LINF = 1e18;
#define dump(x) cout << 'x' << ' = ' << (x) << ` `;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
typedef long long ll;
using namespace std;
typedef pair<ll, ll> P;

template <typename T> void print(const vector<T> &x) {
  int n = x.size();
  rep(i, n) {
    cout << x[i];
    if (i != n - 1)
      cout << " ";
    else
      cout << endl;
  }
}

template <typename T> void print(const vector<vector<T>> &x) {
  int n = x.size();
  rep(i, n) {
    rep(j, x[i].size()) { cout << x[i][j] << " "; }
    cout << endl;
  }
}

template <typename T> void print(const vector<T> &x, int n) {
  rep(i, n) {
    cout << x[i];
    if (i != n - 1)
      cout << " ";
    else
      cout << endl;
  }
}

template <typename T> void print(const vector<vector<T>> &x, int n, int m) {
  rep(i, n) {
    rep(j, m) { cout << x[i][j] << " "; }
    cout << endl;
  }
}

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

void input_init() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}

int main(int argc, char const *argv[]) {
  int h, w, m;
  cin >> h >> w >> m;
  vector<ll> a(m), b(m);
  map<ll, ll> my, mx;
  set<P> st;
  rep(i, m) {
    cin >> a[i] >> b[i];
    st.emplace(a[i], b[i]);
    my[a[i]]++;
    mx[b[i]]++;
  }

  ll Y = 0;
  ll X = 0;
  for (auto &&e : my)
    chmax(Y, e.second);
  for (auto &&e : mx)
    chmax(X, e.second);

  vector<ll> cx, cy;
  for (auto &&e : my)
    if (e.second == Y)
      cy.push_back(e.first);
  for (auto &&e : mx)
    if (e.second == X)
      cx.push_back(e.first);

  ll ans = 0;
  rep(i, cy.size()) {
    rep(j, cx.size()) {
      if (st.count(make_pair(cy[i], cx[j]))) {
        chmax(ans, X + Y - 1);
      } else {
        chmax(ans, X + Y);
      }
    }
  }

  cout << ans << '\n';
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
const int INF = 1e9;
const int MOD = 1e9 + 7;
const long long LINF = 1e18;
#define dump(x) cout << 'x' << ' = ' << (x) << ` `;
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define REPR(i, n) for (int i = n; i >= 0; i--)
#define FOREACH(x, a) for (auto &(x) : (a))
typedef long long ll;
using namespace std;
typedef pair<ll, ll> P;

template <typename T> void print(const vector<T> &x) {
  int n = x.size();
  rep(i, n) {
    cout << x[i];
    if (i != n - 1)
      cout << " ";
    else
      cout << endl;
  }
}

template <typename T> void print(const vector<vector<T>> &x) {
  int n = x.size();
  rep(i, n) {
    rep(j, x[i].size()) { cout << x[i][j] << " "; }
    cout << endl;
  }
}

template <typename T> void print(const vector<T> &x, int n) {
  rep(i, n) {
    cout << x[i];
    if (i != n - 1)
      cout << " ";
    else
      cout << endl;
  }
}

template <typename T> void print(const vector<vector<T>> &x, int n, int m) {
  rep(i, n) {
    rep(j, m) { cout << x[i][j] << " "; }
    cout << endl;
  }
}

template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

void input_init() {
  cin.tie(0);
  ios::sync_with_stdio(false);
}

int main(int argc, char const *argv[]) {
  int h, w, m;
  cin >> h >> w >> m;
  vector<ll> a(m), b(m);
  map<ll, ll> my, mx;
  set<P> st;
  rep(i, m) {
    cin >> a[i] >> b[i];
    st.emplace(a[i], b[i]);
    my[a[i]]++;
    mx[b[i]]++;
  }

  ll Y = 0;
  ll X = 0;
  for (auto &&e : my)
    chmax(Y, e.second);
  for (auto &&e : mx)
    chmax(X, e.second);

  vector<ll> cx, cy;
  for (auto &&e : my)
    if (e.second == Y)
      cy.push_back(e.first);
  for (auto &&e : mx)
    if (e.second == X)
      cx.push_back(e.first);

  ll ans = 0;
  rep(i, cy.size()) {
    rep(j, cx.size()) {
      if (st.count(make_pair(cy[i], cx[j]))) {
        chmax(ans, X + Y - 1);
      } else {
        chmax(ans, X + Y);
        cout << ans << '\n';
        return 0;
      }
    }
  }

  cout << ans << '\n';
  return 0;
}