Problem p03365 (C++)

Buggy submission (status: Time Limit Exceeded):
/* main code starts from line 133. */

/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>

// container library
#include <array>
#include <bitset>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T> using V = vector<T>;
template <typename T, typename U> using P = pair<T, U>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define pb push_back
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define SORT(v) sort(ALL(v))
#define GSORT(v) sort(ALL(v), greater<decltype((v).front())>())

/* ---------- repetition ---------- */

#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define NREP(i, n) FOR(i, 1, n + 1)

#define RFOR(i, a, b) for (ll i = (a); i >= (b); i--)
#define RREP(i, n) RFOR(i, n - 1, 0)
#define RNREP(i, n) RFOR(i, n, 1)

// Usual REP runs from 0 to n-1 (R: n-1 to 0)
// Natural REP runs from 1 to n (R: n to 1)

/* ---------- Short Functions ---------- */

template <typename T> T sq(T a) { return a * a; }

#define fcout cout << fixed << setprecision(10)

/* ----------- debug ---------- */

template <typename T, typename U> void testP2(T a, U b) {
  cout << "(" << a << ", " << b << ")" << endl;
  return;
}

template <typename T> void testV(T v) {
  cout << "[";
  for (auto i : v) {
    cout << i << ", ";
  }
  cout << "\b\b]" << endl;
  return;
}

template <typename T> void testV2(T v) {
  for (auto sv : v) {
    testV(sv);
  }
  cout << endl;
  return;
}

#define GET_VAR_NAME(variable) #variable
#define test(x) cout << GET_VAR_NAME(x) << " = " << x << endl;
#define testP(p)                                                               \
  cout << GET_VAR_NAME(p) << " = ";                                            \
  testP2(p.fst, p.snd);

/* ---------- Constants ---------- */

const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};
// const ll dx[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
// const ll dy[8] = {-1, -1, -1, 0, 0, 1, 1, 1};

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

/* ---------- Type Definition ----------- */

/* ---------- Global Variance ----------- */

const ll MAX_V = 1000010;

/* ------------- Functions -------------- */

V<ll> fact(MAX_V + 1), invfact(MAX_V + 1);

ll calc_pow(ll n, ll k) {
  if (k == 0)
    return 1;
  if (k == 1)
    return n;

  if (k % 2 > 0) {
    return calc_pow(n, k - 1) * n % MOD;
  } else {
    return calc_pow(n * n % MOD, k / 2);
  }
}

void precalc() {
  invfact[0] = fact[0] = 1;
  NREP(i, MAX_V) { fact[i] = fact[i - 1] * i % MOD; }

  invfact[MAX_V] = calc_pow(fact[MAX_V], MOD - 2);
  RREP(i, MAX_V) { invfact[i] = invfact[i + 1] * (i + 1) % MOD; }
  return;
}

ll comb(ll a, ll b) {
  if (a < b)
    return 0;
  if (a == 0)
    return 1; // a = b = 0

  return fact[a] * invfact[a - b] % MOD * invfact[b] % MOD;
}

/* ----------- Main Function ------------ */

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  precalc();

  ll N;
  cin >> N;

  V<ll> pat(N);
  // pat[k] = k台以下で全部塗るパターン数

  REP(k, N) {
    pat[k] = (fact[k] * fact[N - k - 1]) % MOD * comb(k - 1, N - k - 1) % MOD;
  }

  ll ans = 0;
  NREP(k, N - 1) {
    ans += (pat[k] - pat[k - 1]) * k;
    while (ans < 0) {
      ans += MOD;
    }
    ans %= MOD;
  }

  cout << ans << endl;
  return 0;
}

Fixed submission:
/* main code starts from line 133. */

/* ---------- STL Libraries ---------- */

// IO library
#include <cstdio>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>

// container library
#include <array>
#include <bitset>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>

/* ---------- Namespace ---------- */

using namespace std;

/* ---------- Type Abbreviation ---------- */

template <typename T> using V = vector<T>;
template <typename T, typename U> using P = pair<T, U>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using GPQ = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;

#define fst first
#define snd second
#define pb push_back
#define mp make_pair
#define mt make_tuple

/* ---------- conversion ---------- */

#define INT(c) static_cast<int>(c)
#define CHAR(n) static_cast<char>(n)
#define LL(n) static_cast<ll>(n)
#define DOUBLE(n) static_cast<double>(n)

/* ---------- container ---------- */

#define ALL(v) (v).begin(), (v).end()
#define SIZE(v) (LL((v).size()))

#define FIND(v, k) (v).find(k) != (v).end()
#define VFIND(v, k) find(ALL(v), k) != (v).end()

#define SORT(v) sort(ALL(v))
#define GSORT(v) sort(ALL(v), greater<decltype((v).front())>())

/* ---------- repetition ---------- */

#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
#define REP(i, n) FOR(i, 0, n)
#define NREP(i, n) FOR(i, 1, n + 1)

#define RFOR(i, a, b) for (ll i = (a); i >= (b); i--)
#define RREP(i, n) RFOR(i, n - 1, 0)
#define RNREP(i, n) RFOR(i, n, 1)

// Usual REP runs from 0 to n-1 (R: n-1 to 0)
// Natural REP runs from 1 to n (R: n to 1)

/* ---------- Short Functions ---------- */

template <typename T> T sq(T a) { return a * a; }

#define fcout cout << fixed << setprecision(10)

/* ----------- debug ---------- */

template <typename T, typename U> void testP2(T a, U b) {
  cout << "(" << a << ", " << b << ")" << endl;
  return;
}

template <typename T> void testV(T v) {
  cout << "[";
  for (auto i : v) {
    cout << i << ", ";
  }
  cout << "\b\b]" << endl;
  return;
}

template <typename T> void testV2(T v) {
  for (auto sv : v) {
    testV(sv);
  }
  cout << endl;
  return;
}

#define GET_VAR_NAME(variable) #variable
#define test(x) cout << GET_VAR_NAME(x) << " = " << x << endl;
#define testP(p)                                                               \
  cout << GET_VAR_NAME(p) << " = ";                                            \
  testP2(p.fst, p.snd);

/* ---------- Constants ---------- */

const ll MOD = 1e9 + 7;
// const int INF = 1 << 25;
// const ll INF = 1LL << 50;
// const double PI = acos(-1);
// const double EPS = 1e-10;
// const ll dx[4] = {0, -1, 1, 0};
// const ll dy[4] = {-1, 0, 0, 1};
// const ll dx[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
// const ll dy[8] = {-1, -1, -1, 0, 0, 1, 1, 1};

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */

/* ---------- Type Definition ----------- */

/* ---------- Global Variance ----------- */

const ll MAX_V = 1000010;

/* ------------- Functions -------------- */

V<ll> fact(MAX_V + 1), invfact(MAX_V + 1);

ll calc_pow(ll n, ll k) {
  if (k == 0)
    return 1;
  if (k == 1)
    return n;

  if (k % 2 > 0) {
    return calc_pow(n, k - 1) * n % MOD;
  } else {
    return calc_pow(n * n % MOD, k / 2);
  }
}

void precalc() {
  invfact[0] = fact[0] = 1;
  NREP(i, MAX_V) { fact[i] = fact[i - 1] * i % MOD; }

  invfact[MAX_V] = calc_pow(fact[MAX_V], MOD - 2);
  RREP(i, MAX_V) { invfact[i] = invfact[i + 1] * (i + 1) % MOD; }
  return;
}

ll comb(ll a, ll b) {
  if (a < b)
    return 0;
  if (a == 0)
    return 1; // a = b = 0

  return fact[a] * invfact[a - b] % MOD * invfact[b] % MOD;
}

/* ----------- Main Function ------------ */

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  precalc();

  ll N;
  cin >> N;

  V<ll> pat(N);
  // pat[k] = k台以下で全部塗るパターン数

  REP(k, N) {
    pat[k] = (fact[k] * fact[N - k - 1]) % MOD * comb(k - 1, N - k - 1) % MOD;
  }

  ll ans = 0;
  NREP(k, N - 1) {
    ans += (pat[k] - pat[k - 1] + MOD) * k;
    ans %= MOD;
  }

  cout << ans << endl;
  return 0;
}