Problem p02580 (C++)

Buggy submission (status: Time Limit Exceeded):
/*
author : seryu
title : ABC176E_"Bomber"
*/
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define reps(i, n) for (int i = 1; i <= n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define rreps(i, n) for (int i = n; i >= 1; i--)
#define mrep(i, j, n) for (int i = j; i < n; i++)
#define mreps(i, j, n) for (int i = j; i <= n; i++)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ERASE(x, val) x.erase(remove(all(x), val), x.end())
#define MOD 1000000007
typedef long long ll;
typedef pair<int, int> P;
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;
}

// vector<pair<int,int>>の比較関数
bool compare_by_second(pair<int, int> a, pair<int, int> b) {
  if (a.first != b.first)
    return a.first < b.first;
  else
    return a.second < b.second;
}

void solve() {
  int h, w, m;
  cin >> h >> w >> m;
  vector<P> r_sum, c_sum;
  rep(i, h) r_sum.push_back({0, i});
  rep(i, w) c_sum.push_back({0, i});
  vector<P> obj;
  rep(i, m) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    obj.push_back({a, b});
    r_sum[a].first++;
    c_sum[b].first++;
  }
  sort(all(obj));
  sort(all(r_sum));
  reverse(all(r_sum));
  sort(all(c_sum));
  reverse(all(c_sum));
  int ans = 0;
  int i_r = 0, i_c = 0;
  int last_r = r_sum[i_r].first, last_c = c_sum[i_c].first;
  while (true) {
    int tmp = last_r + last_c;
    int r = r_sum[i_r].second;
    int c = c_sum[i_c].second;

    bool cross = false;
    rep(i, m) if (obj[i].first == r && obj[i].second == c) cross = true;
    if (cross)
      tmp--;
    chmax(ans, tmp);
    if (i_r + 1 < h && r_sum[i_r + 1].first == last_r) {
      i_r++;
    } else if (i_c + 1 < w && c_sum[i_c + 1].first == last_c) {
      i_c++;
    } else {
      break;
    }
  }
  cout << ans << endl;
  return;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}


Fixed submission:
/*
author : seryu
title : ABC176E_"Bomber"
*/
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define reps(i, n) for (int i = 1; i <= n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define rreps(i, n) for (int i = n; i >= 1; i--)
#define mrep(i, j, n) for (int i = j; i < n; i++)
#define mreps(i, j, n) for (int i = j; i <= n; i++)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define ERASE(x, val) x.erase(remove(all(x), val), x.end())
#define MOD 1000000007
typedef long long ll;
typedef pair<int, int> P;
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;
}

// vector<pair<int,int>>の比較関数
bool compare_by_second(pair<int, int> a, pair<int, int> b) {
  if (a.first != b.first)
    return a.first < b.first;
  else
    return a.second < b.second;
}

void solve() {
  int h, w, m;
  cin >> h >> w >> m;
  vector<P> r_sum, c_sum;
  rep(i, h) r_sum.push_back({0, i});
  rep(i, w) c_sum.push_back({0, i});
  vector<P> obj;
  rep(i, m) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    obj.push_back({a, b});
    r_sum[a].first++;
    c_sum[b].first++;
  }
  sort(all(obj));
  sort(all(r_sum));
  reverse(all(r_sum));
  sort(all(c_sum));
  reverse(all(c_sum));
  int ans = 0;
  int i_r = 0, i_c = 0;
  int last_r = r_sum[i_r].first, last_c = c_sum[i_c].first;
  while (true) {
    int tmp = last_r + last_c;
    int r = r_sum[i_r].second;
    int c = c_sum[i_c].second;

    bool cross = [&] {
      int left = 0, right = m;
      while (left <= right) {
        int mid = (left + right) / 2;
        if (obj[mid].first == r && obj[mid].second == c)
          return true;
        else if (obj[mid].first < r)
          left = mid + 1;
        else if (obj[mid].first > r)
          right = mid - 1;
        else if (obj[mid].second < c)
          left = mid + 1;
        else
          right = mid - 1;
      }
      return false;
    }();

    if (cross)
      tmp--;
    chmax(ans, tmp);
    if (i_r + 1 < h && r_sum[i_r + 1].first == last_r) {
      i_r++;
    } else if (i_c + 1 < w && c_sum[i_c + 1].first == last_c) {
      i_c++;
    } else {
      break;
    }
  }
  cout << ans << endl;
  return;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}