Problem p02581 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<int> A(3 * N);
  for (int i = 0; i < 3 * N; ++i)
    cin >> A[i], --A[i];

  if (N == 1) {
    cout << (A[0] == A[1] && A[1] == A[2]) << '\\n';
    return 0;
  }

  vector<vector<int>> dp(N + 1, vector<int>(N + 1, -INF)),
      nxt(N + 1, vector<int>(N + 1, -INF));
  vector<int> Max(N, -INF);
  int whole = -INF, same = 0;

  for (int k = 0; k < N - 1; ++k) {
    vector<pair<int, int>> s;
    auto update = [&](int x, int y, int a) {
      nxt[x][y] = max(nxt[x][y], a);
      s.emplace_back(x, y);
    };
    if (!k) {
      for (int i = 0; i < 5; ++i) {
        for (int j = i + 1; j < 5; ++j) {
          set<int> cnt;
          for (int l = 0; l < 5; ++l) {
            if (l != i && l != j) {
              cnt.emplace(A[l]);
            }
          }
          update(A[i], A[j], (cnt.size() == 1));
        }
      }
    } else {
      vector<int> v = {A[3 * k + 2], A[3 * k + 3], A[3 * k + 4]};
      sort(v.begin(), v.end());
      if (v[0] == v[2]) {
        ++same;
        continue;
      }

      for (int i = 0; i < 2; ++i) {
        if (v[i] == v[i + 1]) {
          int rest = (!i ? v[2] : v[0]);
          for (int j = 0; j < N; ++j) {
            update(j, rest, dp[v[i]][j] + 1);
            update(j, rest, dp[j][v[i]] + 1);
          }
        }
      }

      for (int i = 0; i < 3; ++i) {
        vector<int> rest;
        for (int j = 0; j < 3; ++j) {
          if (i != j) {
            rest.emplace_back(v[j]);
          }
        }
        update(rest[0], rest[1], dp[v[i]][v[i]] + 1);
      }

      for (int i = 0; i < N; ++i) {
        for (int j = 0; j < 3; ++j) {
          update(i, v[j], Max[i]);
        }
      }

      for (int i = 0; i < 3; ++i) {
        for (int j = i + 1; j < 3; ++j) {
          update(v[i], v[j], whole);
        }
      }
    }
    for (auto p : s) {
      int x = p.first, y = p.second;
      dp[x][y] = max(dp[x][y], nxt[x][y]);
      Max[x] = max(Max[x], dp[x][y]);
      Max[y] = max(Max[y], dp[x][y]);
    }
    for (int i = 0; i < N; ++i)
      whole = max(whole, Max[i]);
  }

  int ans = 0;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < N; ++j) {
      ans = max(ans, dp[i][j] + (i == A[3 * N - 1] && j == A[3 * N - 1]));
    }
  }
  cout << ans + same << '\\n';
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define LOCAL
#pragma region Macros
typedef long long ll;
#define ALL(x) (x).begin(), (x).end()
const long long MOD = 1e9 + 7;
// const long long MOD=998244353;
const int INF = 1e9;
const long long IINF = 1e18;
const int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const char dir[4] = {'D', 'R', 'U', 'L'};

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < v.size(); ++i) {
    os << v[i] << (i + 1 == v.size() ? "" : " ");
  }
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
  os << '{';
  for (auto itr = m.begin(); itr != m.end(); ++itr) {
    os << '(' << itr->first << ',' << itr->second << ')';
    if (++itr != m.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &s) {
  os << '{';
  for (auto itr = s.begin(); itr != s.end(); ++itr) {
    os << *itr;
    if (++itr != s.end())
      os << ',';
    --itr;
  }
  os << '}';
  return os;
}

void debug_out() { cerr << '\\n'; }
template <class Head, class... Tail>
void debug_out(Head &&head, Tail &&...tail) {
  cerr << head;
  if (sizeof...(Tail) > 0)
    cerr << ", ";
  debug_out(move(tail)...);
}
#ifdef LOCAL
#define debug(...)                                                             \\
  cerr << " ";                                                                 \\
  cerr << #__VA_ARGS__ << " :[" << __LINE__ << ":" << __FUNCTION__ << "]"      \\
       << '\\n';                                                                \\
  cerr << " ";                                                                 \\
  debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

template <typename T> T gcd(T x, T y) { return y != 0 ? gcd(y, x % y) : x; }
template <typename T> T lcm(T x, T y) { return x / gcd(x, y) * y; }

template <class T1, class T2> inline bool chmin(T1 &a, T2 b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T1, class T2> inline bool chmax(T1 &a, T2 b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
#pragma endregion

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int N;
  cin >> N;
  vector<int> A(3 * N);
  for (int i = 0; i < 3 * N; ++i)
    cin >> A[i], --A[i];

  if (N == 1) {
    cout << (A[0] == A[1] && A[1] == A[2]) << '\\n';
    return 0;
  }

  vector<vector<int>> dp(N + 1, vector<int>(N + 1, -INF)),
      nxt(N + 1, vector<int>(N + 1, -INF));
  vector<int> Max(N, -INF);
  int whole = -INF, same = 0;

  for (int k = 0; k < N - 1; ++k) {
    set<pair<int, int>> s;
    auto update = [&](int x, int y, int a) {
      nxt[x][y] = max(nxt[x][y], a);
      s.emplace(x, y);
    };
    if (!k) {
      for (int i = 0; i < 5; ++i) {
        for (int j = i + 1; j < 5; ++j) {
          set<int> cnt;
          for (int l = 0; l < 5; ++l) {
            if (l != i && l != j) {
              cnt.emplace(A[l]);
            }
          }
          update(A[i], A[j], (cnt.size() == 1));
        }
      }
    } else {
      vector<int> v = {A[3 * k + 2], A[3 * k + 3], A[3 * k + 4]};
      sort(v.begin(), v.end());
      if (v[0] == v[2]) {
        ++same;
        continue;
      }

      for (int i = 0; i < 2; ++i) {
        if (v[i] == v[i + 1]) {
          int rest = (!i ? v[2] : v[0]);
          for (int j = 0; j < N; ++j) {
            update(j, rest, dp[v[i]][j] + 1);
            update(j, rest, dp[j][v[i]] + 1);
          }
        }
      }

      for (int i = 0; i < 3; ++i) {
        vector<int> rest;
        for (int j = 0; j < 3; ++j) {
          if (i != j) {
            rest.emplace_back(v[j]);
          }
        }
        update(rest[0], rest[1], dp[v[i]][v[i]] + 1);
      }

      for (int i = 0; i < N; ++i) {
        for (int j = 0; j < 3; ++j) {
          update(i, v[j], Max[i]);
        }
      }

      for (int i = 0; i < 3; ++i) {
        for (int j = i + 1; j < 3; ++j) {
          update(v[i], v[j], whole);
        }
      }
    }
    for (auto p : s) {
      int x = p.first, y = p.second;
      dp[x][y] = max(dp[x][y], nxt[x][y]);
      Max[x] = max(Max[x], dp[x][y]);
      Max[y] = max(Max[y], dp[x][y]);
    }
    for (int i = 0; i < N; ++i)
      whole = max(whole, Max[i]);
  }

  int ans = 0;
  for (int i = 0; i < N; ++i) {
    for (int j = 0; j < N; ++j) {
      ans = max(ans, dp[i][j] + (i == A[3 * N - 1] && j == A[3 * N - 1]));
    }
  }
  cout << ans + same << '\\n';
}