Problem p03365 (C++)

Buggy submission (status: Runtime Error):
#define _USE_MATH_DEFINES
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()                                                              \
  {                                                                            \
    cin.tie(0);                                                                \
    cout.sync_with_stdio(false);                                               \
  }
#define reach(i, a) for (auto i : a)
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define REP(i, n) for (int i = 0; i <= (int)n; i++)
#define srep(i, a, n) for (int i = a; i < (int)n; i++)
#define SREP(i, a, n) for (int i = a; i <= (int)n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, n) for (int i = n; i >= 0; i--)
#define all(a) (a).begin(), (a).end()
#define mp(a, b) make_pair(a, b)
#define mt make_tuple
#define pb push_back
#define fst first
#define scn second
int bitcnt(ll x) {
  x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
  x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
  x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
  x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
  x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
  x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
  return x;
}
int bitcnt(int x) {
  x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
  x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
  x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
  x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
  x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
  return x;
}
ll sqrt(ll x) {
  ll left = 0, right = x;
  rep(i, 100) {
    ll mid = (left + right) >> 1;
    if (mid * mid <= x)
      left = mid;
    else
      right = mid;
  }
  return left;
}
ll gcd(ll a, ll b) { return a % b == 0 ? b : gcd(b, a % b); }
#define debug(x) printf("Case #%d: ", x)
#define DEBUG 0
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;
const int dx[] = {1, 0, -1, 0, 0};
const int dy[] = {0, 1, 0, -1, 0};

ll fact[100010];
ll inv[100010];
ll dp[100010];

ll modpow(ll a, ll b) {
  ll ret = 1;
  while (b) {
    if (b & 1)
      ret = (ret * a) % mod;
    a = (a * a) % mod;
    b >>= 1;
  }
  return ret;
}

ll nCm(ll n, ll m) { return fact[n] * ((inv[m] * inv[n - m]) % mod) % mod; }

int main() {
  int n;
  cin >> n;
  if (n == 2) {
    cout << 1 << endl;
    return 0;
  } else if (n == 3) {
    cout << 4 << endl;
    return 0;
  }
  fact[0] = fact[1] = inv[0] = inv[1] = 1;
  SREP(i, 2, n) {
    fact[i] = (fact[i - 1] * i) % mod;
    inv[i] = (inv[i - 1] * modpow(i, mod - 2)) % mod;
  }
  ll ret = 0;
  srep(i, 2, n) {
    if (i * 2 < n)
      continue;
    dp[i] = ((nCm(i - 1, n - i - 1) * fact[i]) % mod) * fact[n - i - 1] % mod;
    (ret += ((dp[i] - dp[i - 1] + mod) % mod) * i) %= mod;
  }
  cout << ret << endl;
  return 0;
}

Fixed submission:
#define _USE_MATH_DEFINES
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <iostream>
#include <limits>
#include <map>
#include <queue>
#include <random>
#include <regex>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <utility>
#include <vector>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()                                                              \
  {                                                                            \
    cin.tie(0);                                                                \
    cout.sync_with_stdio(false);                                               \
  }
#define reach(i, a) for (auto i : a)
#define rep(i, n) for (int i = 0; i < (int)n; i++)
#define REP(i, n) for (int i = 0; i <= (int)n; i++)
#define srep(i, a, n) for (int i = a; i < (int)n; i++)
#define SREP(i, a, n) for (int i = a; i <= (int)n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define RREP(i, n) for (int i = n; i >= 0; i--)
#define all(a) (a).begin(), (a).end()
#define mp(a, b) make_pair(a, b)
#define mt make_tuple
#define pb push_back
#define fst first
#define scn second
int bitcnt(ll x) {
  x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
  x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
  x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
  x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
  x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
  x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
  return x;
}
int bitcnt(int x) {
  x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
  x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
  x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
  x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
  x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
  return x;
}
ll sqrt(ll x) {
  ll left = 0, right = x;
  rep(i, 100) {
    ll mid = (left + right) >> 1;
    if (mid * mid <= x)
      left = mid;
    else
      right = mid;
  }
  return left;
}
ll gcd(ll a, ll b) { return a % b == 0 ? b : gcd(b, a % b); }
#define debug(x) printf("Case #%d: ", x)
#define DEBUG 0
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ld eps = 1e-9;
const int dx[] = {1, 0, -1, 0, 0};
const int dy[] = {0, 1, 0, -1, 0};

ll fact[1000010];
ll inv[1000010];
ll dp[1000010];

ll modpow(ll a, ll b) {
  ll ret = 1;
  while (b) {
    if (b & 1)
      ret = (ret * a) % mod;
    a = (a * a) % mod;
    b >>= 1;
  }
  return ret;
}

ll nCm(ll n, ll m) { return fact[n] * ((inv[m] * inv[n - m]) % mod) % mod; }

int main() {
  int n;
  cin >> n;
  if (n == 2) {
    cout << 1 << endl;
    return 0;
  } else if (n == 3) {
    cout << 4 << endl;
    return 0;
  }
  fact[0] = fact[1] = inv[0] = inv[1] = 1;
  SREP(i, 2, n) {
    fact[i] = (fact[i - 1] * i) % mod;
    inv[i] = (inv[i - 1] * modpow(i, mod - 2)) % mod;
  }
  ll ret = 0;
  srep(i, 2, n) {
    if (i * 2 < n)
      continue;
    dp[i] = ((nCm(i - 1, n - i - 1) * fact[i]) % mod) * fact[n - i - 1] % mod;
    (ret += ((dp[i] - dp[i - 1] + mod) % mod) * i) %= mod;
  }
  cout << ret << endl;
  return 0;
}