Problem p02580 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;

using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

#define REP(i, l, n) for (int i = (l), i##_len = (n); i < i##_len; ++i)
#define ALL(x) (x).begin(), (x).end()
#define pb push_back

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

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

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

char alpha[26] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                  'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                  's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};

int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, 1, -1};

int main() {
  ll h, w, m;
  cin >> h >> w >> m;
  vector<Pll> H(h, Pll(0, 0)), W(w, Pll(0, 0));
  map<Pll, ll> mp;
  REP(i, 0, h) { H[i].second = i; }
  REP(i, 0, w) { W[i].second = i; }
  REP(i, 0, m) {
    ll x, y;
    cin >> x >> y;
    x--;
    y--;
    H[x].first++;
    W[y].first++;
    mp[Pii(x, y)]++;
  }
  sort(ALL(H), [](auto &x, auto &y) { return x.first > y.first; });
  sort(ALL(W), [](auto &x, auto &y) { return x.first > y.first; });
  ll Hmax = H[0].first, Wmax = W[0].first, i = 0;
  // cout << Hmax << Wmax << endl;
  ll ans = 0;
  while (i < h && Hmax - H[i].first < 1) {
    int l = 0;
    while (l < w && Wmax - W[l].first < 1) {
      if (mp[Pii(H[i].second, W[l].second)] == 1) {
        chmax(ans, H[i].first + W[l].first - 1);
      } else {
        chmax(ans, H[i].first + W[l].first);
      }
      l++;
    }
    i++;
  }
  cout << ans << endl;
}

Fixed submission:
#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;

using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

#define REP(i, l, n) for (int i = (l), i##_len = (n); i < i##_len; ++i)
#define ALL(x) (x).begin(), (x).end()
#define pb push_back

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

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

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

char alpha[26] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i',
                  'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                  's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};

int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, 1, -1};

int main() {
  ll h, w, m;
  cin >> h >> w >> m;
  vector<Pll> H(h, Pll(0, 0)), W(w, Pll(0, 0));
  map<Pll, ll> mp;
  REP(i, 0, h) { H[i].second = i; }
  REP(i, 0, w) { W[i].second = i; }
  REP(i, 0, m) {
    ll x, y;
    cin >> x >> y;
    x--;
    y--;
    H[x].first++;
    W[y].first++;
    mp[Pii(x, y)]++;
  }
  sort(ALL(H), [](auto &x, auto &y) { return x.first > y.first; });
  sort(ALL(W), [](auto &x, auto &y) { return x.first > y.first; });
  ll Hmax = H[0].first, Wmax = W[0].first, i = 0;
  // cout << Hmax << Wmax << endl;
  ll ans = 0;
  while (i < h && Hmax - H[i].first < 1) {
    int l = 0;
    while (l < w && Wmax - W[l].first < 1) {
      if (mp[Pii(H[i].second, W[l].second)] == 1) {
        chmax(ans, H[i].first + W[l].first - 1);
      } else {
        cout << H[i].first + W[l].first << endl;
        return 0;
      }
      l++;
    }
    i++;
  }
  cout << ans << endl;
}