Problem p02728 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>
using namespace std;

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define fi first
#define se second
#define debug(...)                                                             \\
  {                                                                            \\
    cerr << "[L" << __LINE__ << "] ";                                          \\
    _debug(__VA_ARGS__);                                                       \\
  }

template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  for (auto x : v)
    s << del << x;
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) o << (i == 0 ? "[ " : ",\\n  ") << vv[i]
                << (i == l - 1 ? " ]" : "");
  }
  return o;
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const ll INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;
const ll mod = 1e9 + 7;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

struct mint {
  long long x;
  mint(long long x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint &a) {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint &a) {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint &a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint &a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint &a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint &a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint &a) { return (*this) *= a.inv(); }
  mint operator/(const mint &a) const {
    mint res(*this);
    return res /= a;
  }
  friend ostream &operator<<(ostream &os, const mint &m) {
    os << m.x;
    return os;
  }
};
struct Factorial {
  vector<mint> fact;
  vector<mint> factinv;
  Factorial() {}
  Factorial(int n) {
    fact = vector<mint>(n + 1);
    factinv = vector<mint>(n + 1);
    fact[0] = 1;
    REP(i, 1, n + 1) fact[i] = fact[i - 1] * i;
    factinv[n] = fact[n].inv();
    RREP(i, 1, n + 1) factinv[i - 1] = factinv[i] * i;
  }
  mint C(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * factinv[n - k] * factinv[k];
  }
  mint P(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * factinv[n - k];
  }
  mint H(int n, int k) {
    if (n == 0 && k == 0)
      return 1;
    return C(n + k - 1, k);
  }
};

int n;
Factorial f;
vi g[200010];
vector<mint> dp;
vi c;
void dfs1(int v, int p = -1) {
  int total = 0;
  c[0] = 1;
  for (auto u : g[v]) {
    if (u == p)
      continue;
    dfs1(u, v);
    dp[v] *= f.factinv[c[u]] * dp[u];
    total += c[u];
  }
  dp[v] *= f.fact[total];
  c[v] = total + 1;
}

void dfs2(int v, int p = -1) {
  if (p != -1) {
    dp[v] = dp[p] * c[v] * mint(n - c[v]).inv();
  }
  for (auto u : g[v]) {
    if (u == p)
      continue;
    dfs2(u, v);
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  // finput("./input");
  cin >> n;
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    g[a].push_back(b);
    g[b].push_back(a);
  }

  f = Factorial(n);
  dp = vector<mint>(n, 1);
  c = vi(n, 0);
  dfs1(0);
  dfs2(0);
  rep(i, n) cout << dp[i] << endl;
  return 0;
}

Error: 0

Fixed submission:

#include <bits/stdc++.h>
using namespace std;

#define REP(i, m, n) for (int i = (m); i < (int)(n); i++)
#define RREP(i, m, n) for (int i = (int)(n - 1); i >= m; i--)
#define rep(i, n) REP(i, 0, n)
#define rrep(i, n) RREP(i, 0, n)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define fi first
#define se second
#define debug(...)                                                             \\
  {                                                                            \\
    cerr << "[L" << __LINE__ << "] ";                                          \\
    _debug(__VA_ARGS__);                                                       \\
  }

template <typename T> string join(const vector<T> &v, string del = ", ") {
  stringstream s;
  for (auto x : v)
    s << del << x;
  return s.str().substr(del.size());
}
template <typename T> ostream &operator<<(ostream &o, const vector<T> &v) {
  if (v.size())
    o << "[" << join(v) << "]";
  return o;
}
template <typename T>
ostream &operator<<(ostream &o, const vector<vector<T>> &vv) {
  int l = vv.size();
  if (l) {
    o << endl;
    rep(i, l) o << (i == 0 ? "[ " : ",\\n  ") << vv[i]
                << (i == l - 1 ? " ]" : "");
  }
  return o;
}
inline void _debug() { cerr << endl; }
template <class First, class... Rest>
void _debug(const First &first, const Rest &...rest) {
  cerr << first << " ";
  _debug(rest...);
}

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;

const double PI = (1 * acos(0.0));
const double EPS = 1e-9;
const ll INF = 0x3f3f3f3f;
const ll INFL = 0x3f3f3f3f3f3f3f3fLL;
const ll mod = 1e9 + 7;

inline void finput(string filename) { freopen(filename.c_str(), "r", stdin); }

struct mint {
  long long x;
  mint(long long x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint &a) {
    if ((x += a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator-=(const mint &a) {
    if ((x += mod - a.x) >= mod)
      x -= mod;
    return *this;
  }
  mint &operator*=(const mint &a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint &a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint &a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint &a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t)
      return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1)
      a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint &operator/=(const mint &a) { return (*this) *= a.inv(); }
  mint operator/(const mint &a) const {
    mint res(*this);
    return res /= a;
  }
  friend ostream &operator<<(ostream &os, const mint &m) {
    os << m.x;
    return os;
  }
};
struct Factorial {
  vector<mint> fact;
  vector<mint> factinv;
  Factorial() {}
  Factorial(int n) {
    fact = vector<mint>(n + 1);
    factinv = vector<mint>(n + 1);
    fact[0] = 1;
    REP(i, 1, n + 1) fact[i] = fact[i - 1] * i;
    factinv[n] = fact[n].inv();
    RREP(i, 1, n + 1) factinv[i - 1] = factinv[i] * i;
  }
  mint C(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * factinv[n - k] * factinv[k];
  }
  mint P(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * factinv[n - k];
  }
  mint H(int n, int k) {
    if (n == 0 && k == 0)
      return 1;
    return C(n + k - 1, k);
  }
};

int n;
Factorial f;
vi g[100010];
vector<mint> dp;
vi c;
void dfs1(int v, int p = -1) {
  int total = 0;
  c[0] = 1;
  for (auto u : g[v]) {
    if (u == p)
      continue;
    dfs1(u, v);
    dp[v] *= f.factinv[c[u]] * dp[u];
    total += c[u];
  }
  dp[v] *= f.fact[total];
  c[v] = total + 1;
}

void dfs2(int v, int p = -1) {
  if (p != -1) {
    dp[v] = dp[p] * c[v] * mint(n - c[v]).inv();
  }
  for (auto u : g[v]) {
    if (u == p)
      continue;
    dfs2(u, v);
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  // finput("./input");
  cin >> n;
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    g[a].push_back(b);
    g[b].push_back(a);
  }

  f = Factorial(n);
  dp = vector<mint>(n, 1);
  c = vi(n, 0);
  dfs1(0);
  dfs2(0);
  rep(i, n) cout << dp[i] << endl;
  return 0;
}