Problem p02580 (C++) — buggy submission, verdict: Time Limit Exceeded

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

#define ms(s, n) memset(s, n, sizeof(s))
#define f(i, a, b) for (int i = (a); i <= (b); i++)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); i--)
#define FORall(it, a)                                                          \\
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
#define IOS                                                                    \\
  ios::sync_with_stdio(0);                                                     \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<ll> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int MOD2 = MOD + 2; // 1007681537;
const int INF = (int)1e9;
const ll LINF = (ll)1e18;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ll isqrt(ll k) {
  ll r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
int modulo(int a, int b) { return (a % b + b) % b; }
#define db(x) cerr << #x << " = " << (x) << " ";
#define endln cerr << "\\n";

int main() {
  IOS;
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  int h, w, m;
  cin >> h >> w >> m;
  vector<int> rowsum(h + 1, 0), colsum(w + 1, 0);
  set<pair<int, int>> s;
  f(i, 0, m - 1) {
    int x, y;
    cin >> x >> y;
    rowsum[x]++;
    colsum[y]++;
    s.insert({x, y});
  }
  // vector<vector<int>> val(h + 1, vector<int>(w + 1, 0));
  vector<pair<int, int>> vh, ch, vf, cf;
  f(i, 1, h) { vh.pb({rowsum[i], i}); }
  f(i, 1, w) { ch.pb({colsum[i], i}); }
  sort(vh.begin(), vh.end());
  reverse(vh.begin(), vh.end());
  sort(ch.begin(), ch.end());
  reverse(ch.begin(), ch.end());
  vf.pb(vh[0]);
  cf.pb(ch[0]);
  int i = 1;
  while (i <= h - 1 && vh[i].fi == vh[0].fi) {
    vf.pb(vh[i]);
    i++;
  }
  i = 1;
  while (i <= w - 1 && ch[i].fi == ch[0].fi) {
    cf.pb(ch[i]);
    i++;
  }
  int ans = 0;
  bool ok = true;
  int fval = vf[0].fi + cf[0].fi;
  for (auto p : vf) {
    for (auto q : cf) {
      int val = p.fi + q.fi;
      if (s.find({p.se, q.se}) != s.end()) {
        val--;
      }
      ans = max(ans, val);
      if (val == fval) {
        ok = false;
        break;
      }
    }
    if (!ok)
      break;
  }
  cout << ans << endl;
  // read the stuff at the bottom
  return 0;
}
/* stuff you should look for
 * int overflow, array bounds
 * special cases (n=1?)
 * do smth instead of nothing and stay organized
 * WRITE STUFF DOWN
 * use int when constraints limits are tight
 * Time taken : global variable < pass by refernce < pass by value
 * It takes significant amt. of time in pass by value
 */


Error: TLE

Fixed submission:

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

#define ms(s, n) memset(s, n, sizeof(s))
#define f(i, a, b) for (int i = (a); i <= (b); i++)
#define FORd(i, a, b) for (int i = (a)-1; i >= (b); i--)
#define FORall(it, a)                                                          \\
  for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed << setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
#define IOS                                                                    \\
  ios::sync_with_stdio(0);                                                     \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<ll> vi;
typedef vector<pi> vii;
const int MOD = (int)1e9 + 7;
const int MOD2 = MOD + 2; // 1007681537;
const int INF = (int)1e9;
const ll LINF = (ll)1e18;
const ld PI = acos((ld)-1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {
  ll r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
inline ll fpow(ll n, ll k, int p = MOD) {
  ll r = 1;
  for (; k; k >>= 1) {
    if (k & 1)
      r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T> inline int chkmin(T &a, const T &val) {
  return val < a ? a = val, 1 : 0;
}
template <class T> inline int chkmax(T &a, const T &val) {
  return a < val ? a = val, 1 : 0;
}
inline ll isqrt(ll k) {
  ll r = sqrt(k) + 1;
  while (r * r > k)
    r--;
  return r;
}
inline ll icbrt(ll k) {
  ll r = cbrt(k) + 1;
  while (r * r * r > k)
    r--;
  return r;
}
inline void addmod(int &a, int val, int p = MOD) {
  if ((a = (a + val)) >= p)
    a -= p;
}
inline void submod(int &a, int val, int p = MOD) {
  if ((a = (a - val)) < 0)
    a += p;
}
inline int mult(int a, int b, int p = MOD) { return (ll)a * b % p; }
inline int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
inline int sign(ld x) { return x < -EPS ? -1 : x > +EPS; }
inline int sign(ld x, ld y) { return sign(x - y); }
int modulo(int a, int b) { return (a % b + b) % b; }
#define db(x) cerr << #x << " = " << (x) << " ";
#define endln cerr << "\\n";

int main() {
  IOS;
#ifndef ONLINE_JUDGE
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  int h, w, m;
  cin >> h >> w >> m;
  vector<int> rowsum(h + 1, 0), colsum(w + 1, 0);
  set<pair<int, int>> s;
  f(i, 0, m - 1) {
    int x, y;
    cin >> x >> y;
    rowsum[x]++;
    colsum[y]++;
    s.insert({x, y});
  }
  // vector<vector<int>> val(h + 1, vector<int>(w + 1, 0));
  vector<pair<int, int>> vh, ch, vf, cf;
  f(i, 1, h) { vh.pb({rowsum[i], i}); }
  f(i, 1, w) { ch.pb({colsum[i], i}); }
  sort(vh.begin(), vh.end());
  reverse(vh.begin(), vh.end());
  sort(ch.begin(), ch.end());
  reverse(ch.begin(), ch.end());
  vf.pb(vh[0]);
  cf.pb(ch[0]);
  int i = 1;
  while (i <= h - 1 && vh[i].fi == vh[0].fi) {
    vf.pb(vh[i]);
    i++;
  }
  i = 1;
  while (i <= w - 1 && ch[i].fi == ch[0].fi) {
    cf.pb(ch[i]);
    i++;
  }
  int ans = 0;
  for (auto p : vf) {
    for (auto q : cf) {
      int val = p.fi + q.fi;
      if (s.find({p.se, q.se}) != s.end()) {
        val--;
      }
      ans = max(ans, val);
    }
  }
  cout << ans << endl;
  // read the stuff at the bottom
  return 0;
}
/* stuff you should look for
 * int overflow, array bounds
 * special cases (n=1?)
 * do smth instead of nothing and stay organized
 * WRITE STUFF DOWN
 * use int when constraints limits are tight
 * Time taken : global variable < pass by refernce < pass by value
 * It takes significant amt. of time in pass by value
 */