Problem p02850 (C++)

Buggy submission (status: Time Limit Exceeded):
// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rep1(i, n) for (int i = 1; i <= int(n); i++)
#define repR(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define rep1R(i, n) for (int i = int(n); i >= 1; i--)
#define loop(i, a, B) for (int i = a; i B; i++)
#define loopR(i, a, B) for (int i = a; i B; i--)
#define all(x) (x).begin(), (x).end()
#define allR(x) (x).rbegin(), (x).rend()
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
#ifdef LOCAL
#define dump(...)                                                              \
  cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] ",                      \
      dump_impl(#__VA_ARGS__, __VA_ARGS__)
#define say(x)                                                                 \
  cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] " << x << endl;
#define debug if (1)
void dump_impl(const char *) { cerr << endl; }
template <class T, class... U>
void dump_impl(const char *s, T const &x, U const &...y) {
  const char *o = "({[", *e = "]})";
  for (int i = 0; *s != '\0'; cerr << *s++) {
    if (count(o, o + 3, *s))
      i++;
    if (count(e, e + 3, *s))
      i--;
    if (!i && *s == ',')
      break;
  }
  cerr << " = " << x;
  if (*s == ',')
    cerr << ", ", s++;
  dump_impl(s, y...);
}
#else
#define dump(...)
#define say(x)
#define debug if (0)
#endif
using ll = long long;
using ld = long double;
#define int ll
#define double ld
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T>>;
template <class T, class = typename T::iterator,
          class = typename enable_if<!is_same<T, string>::value>::type>
ostream &operator<<(ostream &os, T const &v) {
  os << "{";
  for (auto const &x : v)
    os << " " << x;
  return os << " }";
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <class T, class S>
ostream &operator<<(ostream &os, pair<T, S> const &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
template <class T, class S> istream &operator>>(istream &is, pair<T, S> &p) {
  return is >> p.first >> p.second;
}
template <size_t i, class T>
typename enable_if<i >= tuple_size<T>::value>::type output_tuple(ostream &,
                                                                 T const &) {}
template <size_t i = 0, class T>
    typename enable_if <
    i<tuple_size<T>::value>::type output_tuple(ostream &os, T const &t) {
  os << (i ? " " : "") << get<i>(t);
  output_tuple<i + 1, T>(os, t);
}
template <class... T> ostream &operator<<(ostream &os, tuple<T...> const &t) {
  return output_tuple(os, t), os;
}
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
  }
} iosetup;
template <class T, size_t d> struct vec_impl {
  using type = vector<typename vec_impl<T, d - 1>::type>;
  template <class... U> static type make_v(size_t n, U &&...x) {
    return type(n, vec_impl<T, d - 1>::make_v(forward<U>(x)...));
  }
};
template <class T> struct vec_impl<T, 0> {
  using type = T;
  static type make_v(T const &x = {}) { return x; }
};
template <class T, size_t d = 1> using vec = typename vec_impl<T, d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args &&...args) {
  return vec_impl<T, d>::make_v(forward<Args>(args)...);
}
template <class T> void quit(T const &x) {
  cout << x << endl;
  exit(0);
}
template <class T> constexpr bool chmin(T &x, T const &y) {
  if (x > y) {
    x = y;
    return true;
  }
  return false;
}
template <class T> constexpr bool chmax(T &x, T const &y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}
template <class It> constexpr auto sumof(It b, It e) {
  return accumulate(b, e, typename iterator_traits<It>::value_type{});
}
const ll INF = (1LL << 62) - 1; // ~ 4.6e18
// <<<
int n;
struct edge {
  int id, to;
};
vec<edge, 2> g;
vector<int> c;
int k;

void dfs(int x, int p = -1, int pc = -1) {
  queue<int> cs;
  rep(i, k) if (i != pc) cs.push(i);
  for (auto e : g[x]) {
    if (e.to == p)
      continue;
    c[e.id] = cs.front();
    cs.pop();
    dfs(e.to, x, c[e.id]);
  }
}

int32_t main() {
  cin >> n;
  g.resize(n);
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    g[a].eb(edge{i, b});
    g[b].eb(edge{i, a});
  }
  k = 0;
  rep(i, n) chmax(k, (int)g[i].size());
  c.resize(n - 1, -1);
  dfs(0);
  cout << k << "\n";
  rep(i, n - 1) cout << c[i] + 1 << "\n";
}


Fixed submission:
// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < int(n); i++)
#define rep1(i, n) for (int i = 1; i <= int(n); i++)
#define repR(i, n) for (int i = int(n) - 1; i >= 0; i--)
#define rep1R(i, n) for (int i = int(n); i >= 1; i--)
#define loop(i, a, B) for (int i = a; i B; i++)
#define loopR(i, a, B) for (int i = a; i B; i--)
#define all(x) (x).begin(), (x).end()
#define allR(x) (x).rbegin(), (x).rend()
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
#ifdef LOCAL
#define dump(...)                                                              \
  cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] ",                      \
      dump_impl(#__VA_ARGS__, __VA_ARGS__)
#define say(x)                                                                 \
  cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] " << x << endl;
#define debug if (1)
void dump_impl(const char *) { cerr << endl; }
template <class T, class... U>
void dump_impl(const char *s, T const &x, U const &...y) {
  const char *o = "({[", *e = "]})";
  for (int i = 0; *s != '\0'; cerr << *s++) {
    if (count(o, o + 3, *s))
      i++;
    if (count(e, e + 3, *s))
      i--;
    if (!i && *s == ',')
      break;
  }
  cerr << " = " << x;
  if (*s == ',')
    cerr << ", ", s++;
  dump_impl(s, y...);
}
#else
#define dump(...)
#define say(x)
#define debug if (0)
#endif
using ll = long long;
using ld = long double;
#define int ll
#define double ld
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T>>;
template <class T, class = typename T::iterator,
          class = typename enable_if<!is_same<T, string>::value>::type>
ostream &operator<<(ostream &os, T const &v) {
  os << "{";
  for (auto const &x : v)
    os << " " << x;
  return os << " }";
}
template <class T> istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v)
    is >> x;
  return is;
}
template <class T, class S>
ostream &operator<<(ostream &os, pair<T, S> const &p) {
  return os << "(" << p.first << ", " << p.second << ")";
}
template <class T, class S> istream &operator>>(istream &is, pair<T, S> &p) {
  return is >> p.first >> p.second;
}
template <size_t i, class T>
typename enable_if<i >= tuple_size<T>::value>::type output_tuple(ostream &,
                                                                 T const &) {}
template <size_t i = 0, class T>
    typename enable_if <
    i<tuple_size<T>::value>::type output_tuple(ostream &os, T const &t) {
  os << (i ? " " : "") << get<i>(t);
  output_tuple<i + 1, T>(os, t);
}
template <class... T> ostream &operator<<(ostream &os, tuple<T...> const &t) {
  return output_tuple(os, t), os;
}
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
  }
} iosetup;
template <class T, size_t d> struct vec_impl {
  using type = vector<typename vec_impl<T, d - 1>::type>;
  template <class... U> static type make_v(size_t n, U &&...x) {
    return type(n, vec_impl<T, d - 1>::make_v(forward<U>(x)...));
  }
};
template <class T> struct vec_impl<T, 0> {
  using type = T;
  static type make_v(T const &x = {}) { return x; }
};
template <class T, size_t d = 1> using vec = typename vec_impl<T, d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args &&...args) {
  return vec_impl<T, d>::make_v(forward<Args>(args)...);
}
template <class T> void quit(T const &x) {
  cout << x << endl;
  exit(0);
}
template <class T> constexpr bool chmin(T &x, T const &y) {
  if (x > y) {
    x = y;
    return true;
  }
  return false;
}
template <class T> constexpr bool chmax(T &x, T const &y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}
template <class It> constexpr auto sumof(It b, It e) {
  return accumulate(b, e, typename iterator_traits<It>::value_type{});
}
const ll INF = (1LL << 62) - 1; // ~ 4.6e18
// <<<
int n;
struct edge {
  int id, to;
};
vec<edge, 2> g;
vector<int> c;
int k;

void dfs(int x, int p = -1, int pc = -1) {
  queue<int> cs;
  rep(i, k) {
    if (i != pc)
      cs.push(i);
    if (cs.size() >= g[x].size())
      break;
  }
  for (auto e : g[x]) {
    if (e.to == p)
      continue;
    c[e.id] = cs.front();
    cs.pop();
    dfs(e.to, x, c[e.id]);
  }
}

int32_t main() {
  cin >> n;
  g.resize(n);
  rep(i, n - 1) {
    int a, b;
    cin >> a >> b;
    a--, b--;
    g[a].eb(edge{i, b});
    g[b].eb(edge{i, a});
  }
  k = 0;
  rep(i, n) chmax(k, (int)g[i].size());
  c.resize(n - 1, -1);
  dfs(0);
  cout << k << "\n";
  rep(i, n - 1) cout << c[i] + 1 << "\n";
}