Problem p02581 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \\
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \\
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \\
  {                                                                            \\
    cout << #v << "=" << endl;                                                 \\
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \\
    cout << endl;                                                              \\
  }
#define mdebug(m)                                                              \\
  {                                                                            \\
    cout << #m << "=" << endl;                                                 \\
    REP(i_debug, m.size()) {                                                   \\
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \\
      cout << endl;                                                            \\
    }                                                                          \\
  }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void chOut(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PPi = pair<Pii, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;
using v_PPi = vector<PPi>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;

signed main() {

  int N;
  cin >> N;
  vec A(3 * N);
  cin >> A;
  REP(i, 3 * N) A[i]--;

  mat dp(N, vec(N, -INF));
  vec dpMAX(N, -INF);
  int offset = 0;
  dp[A[0]][A[1]] = dp[A[1]][A[0]] = 0;
  dpMAX[A[0]] = 0;
  dpMAX[A[1]] = 0;
  int allMAX = 0;

  REP(i, N - 1) {
    vec v({A[3 * i + 2], A[3 * i + 3], A[3 * i + 4]});
    Sort(v);

    v_PPi ls;
    if (v[0] == v[2]) {
      offset++;
      continue;
    } else if (v[0] == v[1]) {
      REP(k, N) { ls.pb(PPi(Pii(k, v[2]), dp[k][v[0]] + 1)); }
    } else if (v[1] == v[2]) {
      REP(k, N) { ls.pb(PPi(Pii(k, v[0]), dp[k][v[1]] + 1)); }
    }
    REP(k, 3) {
      ls.pb(PPi(Pii(v[(k + 1) % 3], v[(k + 2) % 3]), dp[v[k]][v[k]] + 1));

      REP(l, N) ls.pb(PPi(Pii(l, v[k]), dpMAX[l]));
      ls.pb(PPi(Pii(v[(k + 1) % 3], v[(k + 2) % 3]), allMAX));
    }

    for (PPi q : ls) {
      chmax(dp[q.fi.fi][q.fi.se], q.se);
      chmax(dp[q.fi.se][q.fi.fi], q.se);
      chmax(dpMAX[q.fi.fi], q.se);
      chmax(dpMAX[q.fi.se], q.se);
      chmax(allMAX, q.se);
    }
  }

  int ans = 0;
  REP(i, N)
  REP(j, N) chmax(ans, dp[i][j] + (i == A[3 * N - 1] && j == A[3 * N - 1]));
  ans += offset;
  Out(ans);

  return 0;
}


Error: 0

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
struct fast_ios {
  fast_ios() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  };
} fast_ios_;
#define FOR(i, begin, end) for (int i = (begin); i < (end); i++)
#define REP(i, n) FOR(i, 0, n)
#define IFOR(i, begin, end) for (int i = (end)-1; i >= (begin); i--)
#define IREP(i, n) IFOR(i, 0, n)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define all(v) v.begin(), v.end()
#define SZ(v) ((int)v.size())
#define Lower_bound(v, x)                                                      \\
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x)                                                      \\
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define bit(n) (1LL << (n))
#define debug(x) cout << #x << "=" << x << endl;
#define vdebug(v)                                                              \\
  {                                                                            \\
    cout << #v << "=" << endl;                                                 \\
    REP(i_debug, v.size()) { cout << v[i_debug] << ","; }                      \\
    cout << endl;                                                              \\
  }
#define mdebug(m)                                                              \\
  {                                                                            \\
    cout << #m << "=" << endl;                                                 \\
    REP(i_debug, m.size()) {                                                   \\
      REP(j_debug, m[i_debug].size()) { cout << m[i_debug][j_debug] << ","; }  \\
      cout << endl;                                                            \\
    }                                                                          \\
  }
#define pb push_back
#define fi first
#define se second
#define int long long
#define INF 1000000000000000000
template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <typename T> ostream &operator<<(ostream &os, vector<T> &v) {
  for (int i = 0; i < v.size(); i++) {
    cout << v[i];
    if (i != v.size() - 1)
      cout << endl;
  };
  return os;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, pair<T1, T2> p) {
  cout << '(' << p.first << ',' << p.second << ')';
  return os;
}
template <typename T> void Out(T x) { cout << x << endl; }
template <typename T1, typename T2> void chOut(bool f, T1 y, T2 n) {
  if (f)
    Out(y);
  else
    Out(n);
}

using vec = vector<int>;
using mat = vector<vec>;
using Pii = pair<int, int>;
using PPi = pair<Pii, int>;
using v_bool = vector<bool>;
using v_Pii = vector<Pii>;
using v_PPi = vector<PPi>;

// int dx[4] = {1,0,-1,0};
// int dy[4] = {0,1,0,-1};
// char d[4] = {'D','R','U','L'};

const int mod = 1000000007;
// const int mod = 998244353;

signed main() {

  int N;
  cin >> N;
  vec A(3 * N);
  cin >> A;
  REP(i, 3 * N) A[i]--;

  mat dp(N, vec(N, -INF));
  vec dpMAX(N, -INF);
  int allMAX = -INF;
  int offset = 0;
  dp[A[0]][A[1]] = dp[A[1]][A[0]] = 0;
  REP(i, N - 1) {
    vec v({A[3 * i + 2], A[3 * i + 3], A[3 * i + 4]});
    Sort(v);

    v_PPi ls;
    if (v[0] == v[2]) {
      offset++;
      exit(1);
      continue;
    } else if (v[0] == v[1]) {
      REP(k, N) { ls.pb(PPi(Pii(k, v[2]), dp[k][v[0]] + 1)); }
    } else if (v[1] == v[2]) {
      REP(k, N) { ls.pb(PPi(Pii(k, v[0]), dp[k][v[1]] + 1)); }
    }
    REP(k, 3) {
      ls.pb(PPi(Pii(v[(k + 1) % 3], v[(k + 2) % 3]), dp[v[k]][v[k]] + 1));

      REP(l, N) ls.pb(PPi(Pii(l, v[k]), dpMAX[l]));
      ls.pb(PPi(Pii(v[(k + 1) % 3], v[(k + 2) % 3]), allMAX));
    }

    for (PPi q : ls) {
      chmax(dp[q.fi.fi][q.fi.se], q.se);
      chmax(dp[q.fi.se][q.fi.fi], q.se);
      chmax(dpMAX[q.fi.fi], q.se);
      chmax(dpMAX[q.fi.se], q.se);
      chmax(allMAX, q.se);
    }
  }

  int ans = 0;
  REP(i, N)
  REP(j, N) chmax(ans, dp[i][j] + (i == A[3 * N - 1] && j == A[3 * N - 1]));
  ans += offset;
  Out(ans);

  return 0;
}