Problem p03855 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

/* define */
#define FOR(I, X, Y) for (long long(I) = (X); (I) < (Y); (I)++)
#define REP(I, X, Y) for (long long(I) = (Y)-1; (I) >= (X); (I)--)
#define ALL(X) (X).begin(), (X).end()
#define pb push_back
#define COUNT(V, X)                                                            \
  upper_bound((V).begin(), (V).end(), X) -                                     \
      lower_bound((V).begin(), (V).end(), X)
#define debug(x) cerr << #x << ':' << x << endl;
#define DEBUG(v)                                                               \
  cerr << #v << ':';                                                           \
  for (auto xXx : v)                                                           \
    cerr << xXx << ' ';                                                        \
  cerr << endl;
#define Yes(X)                                                                 \
  if (X) {                                                                     \
    cout << "Yes" << endl;                                                     \
  } else {                                                                     \
    cout << "No" << endl;                                                      \
  }
#define YES(X)                                                                 \
  if (X) {                                                                     \
    cout << "YES" << endl;                                                     \
  } else {                                                                     \
    cout << "NO" << endl;                                                      \
  }
#define ctoi(C) (C - '0')

/* alias */
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<long long>;
using vll = vector<vector<long long>>;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const long long dx[] = {1, 0, -1, 0};
const long long dy[] = {0, 1, 0, -1};
const long long dx8[] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long dx9[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};
const int INF = 1000000007;
const long long LINF = 1000000000000000007;

/* func */
template <typename T> inline bool chmin(T &a, const T &b) {
  if (a > b)
    a = b;
  return a > b;
}
template <typename T> inline bool chmax(T &a, const T &b) {
  if (a < b)
    a = b;
  return a < b;
}
long long max(long long x, int y) { return max(x, (long long)y); }
long long max(int x, long long y) { return max((long long)x, y); }
long long min(long long x, int y) { return min(x, (long long)y); }
long long min(int x, long long y) { return min((long long)x, y); }

/* liblary */

struct UnionFind {
  vector<long long> data;
  UnionFind(long long N) : data(vector<long long>(N, -1)) {}
  void boot(long long n) {
    for (long long i = 0; i < n; i++)
      data.push_back(-1);
    return;
  }
  long long root(long long x) {
    if (data[x] < 0)
      return x;
    else
      return data[x] = root(data[x]);
  }
  bool same(long long x, long long y) { return root(x) == root(y); }
  void unite(long long x, long long y) {
    if (!same(x, y)) {
      x = root(x);
      y = root(y);
      if (data[x] < data[y]) {
        data[x] += data[y];
        data[y] = x;
      } else {
        data[y] += data[x];
        data[x] = y;
      }
    }
    return;
  }
  long long getsize(long long x) { return -data[root(x)]; }
};

/* main */

signed main() {
  ll N, K, L;
  cin >> N >> K >> L;
  UnionFind train(N);
  UnionFind road(N);
  FOR(i, 0, K) {
    ll p, q;
    cin >> p >> q;
    road.unite(p - 1, q - 1);
  }
  FOR(i, 0, L) {
    ll r, s;
    cin >> r >> s;
    train.unite(r - 1, s - 1);
  }
  multiset<pl> s;
  FOR(i, 0, N) s.insert(make_pair(road.root(i), train.root(i)));
  FOR(i, 0, N) {
    cout << s.count(make_pair(road.root(i), train.root(i))) << ' ';
  }
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

/* define */
#define FOR(I, X, Y) for (long long(I) = (X); (I) < (Y); (I)++)
#define REP(I, X, Y) for (long long(I) = (Y)-1; (I) >= (X); (I)--)
#define ALL(X) (X).begin(), (X).end()
#define pb push_back
#define COUNT(V, X)                                                            \
  upper_bound((V).begin(), (V).end(), X) -                                     \
      lower_bound((V).begin(), (V).end(), X)
#define debug(x) cerr << #x << ':' << x << endl;
#define DEBUG(v)                                                               \
  cerr << #v << ':';                                                           \
  for (auto xXx : v)                                                           \
    cerr << xXx << ' ';                                                        \
  cerr << endl;
#define Yes(X)                                                                 \
  if (X) {                                                                     \
    cout << "Yes" << endl;                                                     \
  } else {                                                                     \
    cout << "No" << endl;                                                      \
  }
#define YES(X)                                                                 \
  if (X) {                                                                     \
    cout << "YES" << endl;                                                     \
  } else {                                                                     \
    cout << "NO" << endl;                                                      \
  }
#define ctoi(C) (C - '0')

/* alias */
using ll = long long;
using ld = long double;
using vi = vector<int>;
using vii = vector<vector<int>>;
using vl = vector<long long>;
using vll = vector<vector<long long>>;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const long long dx[] = {1, 0, -1, 0};
const long long dy[] = {0, 1, 0, -1};
const long long dx8[] = {1, 1, 0, -1, -1, -1, 0, 1};
const long long dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long dx9[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};
const int INF = 1000000007;
const long long LINF = 1000000000000000007;

/* func */
template <typename T> inline bool chmin(T &a, const T &b) {
  if (a > b)
    a = b;
  return a > b;
}
template <typename T> inline bool chmax(T &a, const T &b) {
  if (a < b)
    a = b;
  return a < b;
}
long long max(long long x, int y) { return max(x, (long long)y); }
long long max(int x, long long y) { return max((long long)x, y); }
long long min(long long x, int y) { return min(x, (long long)y); }
long long min(int x, long long y) { return min((long long)x, y); }

/* liblary */

struct UnionFind {
  vector<long long> data;
  UnionFind(long long N) : data(vector<long long>(N, -1)) {}
  void boot(long long n) {
    for (long long i = 0; i < n; i++)
      data.push_back(-1);
    return;
  }
  long long root(long long x) {
    if (data[x] < 0)
      return x;
    else
      return data[x] = root(data[x]);
  }
  bool same(long long x, long long y) { return root(x) == root(y); }
  void unite(long long x, long long y) {
    if (!same(x, y)) {
      x = root(x);
      y = root(y);
      if (data[x] < data[y]) {
        data[x] += data[y];
        data[y] = x;
      } else {
        data[y] += data[x];
        data[x] = y;
      }
    }
    return;
  }
  long long getsize(long long x) { return -data[root(x)]; }
};

/* main */

signed main() {
  ll N, K, L;
  cin >> N >> K >> L;
  UnionFind train(N);
  UnionFind road(N);
  FOR(i, 0, K) {
    ll p, q;
    cin >> p >> q;
    road.unite(p - 1, q - 1);
  }
  FOR(i, 0, L) {
    ll r, s;
    cin >> r >> s;
    train.unite(r - 1, s - 1);
  }
  map<pl, ll> m;
  FOR(i, 0, N) m[make_pair(road.root(i), train.root(i))]++;
  FOR(i, 0, N) { cout << m[make_pair(road.root(i), train.root(i))] << ' '; }
}