Problem p01138 (C++)

Buggy submission (status: Time Limit Exceeded):
#include "bits/stdc++.h"

#define REP(i, n) for (ll i = 0; i < n; ++i)
#define RREP(i, n) for (ll i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (ll i = m; i < n; ++i)
#define RFOR(i, m, n) for (ll i = n - 1; i >= m; --i)
#define ALL(v) (v).begin(), (v).end()
#define PB(a) push_back(a)
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end());
#define DUMP(v)                                                                \
  REP(aa, (v).size()) {                                                        \
    cout << v[a];                                                              \
    if (a != v.size() - 1)                                                     \
      cout << " ";                                                             \
    else                                                                       \
      cout << endl;                                                            \
  }
#define INF 1000000001ll
#define MOD 1000000007ll
#define EPS 1e-9

const int dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};

using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
ll max(ll a, int b) { return max(a, ll(b)); }
ll max(int a, ll b) { return max(ll(a), b); }
ll min(ll a, int b) { return min(a, ll(b)); }
ll min(int a, ll b) { return min(ll(a), b); }
///(?´????????`)(?´????????`)(?´????????`)(?´????????`)(?´????????`)(?´????????`)///
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  while (1) {
    int n;
    cin >> n;
    if (!n)
      break;
    vi v(24 * 60 * 60 + 1, 0);
    REP(i, n) {
      int h, m, s;
      char c;
      cin >> h >> c >> m >> c >> s;
      v[h * 60 * 60 + m * 60 + s]++;
      cin >> h >> c >> m >> c >> s;
      v[h * 60 * 60 + m * 60 + s]--;
    }
    REP(i, 24 * 60 * 60) { cout << *max_element(ALL(v)) << endl; }
  }
  return 0;
}

Fixed submission:
#include "bits/stdc++.h"

#define REP(i, n) for (ll i = 0; i < n; ++i)
#define RREP(i, n) for (ll i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (ll i = m; i < n; ++i)
#define RFOR(i, m, n) for (ll i = n - 1; i >= m; --i)
#define ALL(v) (v).begin(), (v).end()
#define PB(a) push_back(a)
#define UNIQUE(v) v.erase(unique(ALL(v)), v.end());
#define DUMP(v)                                                                \
  REP(aa, (v).size()) {                                                        \
    cout << v[a];                                                              \
    if (a != v.size() - 1)                                                     \
      cout << " ";                                                             \
    else                                                                       \
      cout << endl;                                                            \
  }
#define INF 1000000001ll
#define MOD 1000000007ll
#define EPS 1e-9

const int dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const int dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};

using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
ll max(ll a, int b) { return max(a, ll(b)); }
ll max(int a, ll b) { return max(ll(a), b); }
ll min(ll a, int b) { return min(a, ll(b)); }
ll min(int a, ll b) { return min(ll(a), b); }
///(?´????????`)(?´????????`)(?´????????`)(?´????????`)(?´????????`)(?´????????`)///
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  while (1) {
    int n;
    cin >> n;
    if (!n)
      break;
    vi v(24 * 60 * 60 + 1, 0);
    REP(i, n) {
      int h, m, s;
      char c;
      cin >> h >> c >> m >> c >> s;
      v[h * 60 * 60 + m * 60 + s]++;
      cin >> h >> c >> m >> c >> s;
      v[h * 60 * 60 + m * 60 + s]--;
    }
    REP(i, 24 * 60 * 60) { v[i + 1] += v[i]; }
    cout << *max_element(ALL(v)) << endl;
  }
  return 0;
}