Problem p02558 (C++) — buggy submission, verdict: Runtime Error

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

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef long long LL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef vector<bool> VB;
typedef vector<VB> VVB;
typedef vector<double> VD;
typedef vector<VD> VVD;
typedef vector<string> VS;
typedef vector<VS> VVS;
typedef vector<char> VC;
typedef vector<VC> VVC;
typedef vector<PII> VPII;
typedef vector<PLL> VPLL;
typedef priority_queue<int> PQGI; // 大きい順
typedef priority_queue<int, VI, greater<int>> PQLI;
typedef priority_queue<PII> PQGP;
typedef priority_queue<PII, VPII, greater<PII>> PQLP;
// priority_queue<T,vector<T>,decltype(f)> pq{f};

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EB emplace_back
#define EF emplace_front
#define PB push_back
#define PF push_front
#define POB pop_back
#define POF pop_front
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a) * (a))
#define EACH(i, c)                                                             \\
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define SORTR(c) sort((c).rbegin(), (c).rend())
#define LB lower_bound
#define UB upper_bound
#define NEXP next_permutation
#define FI first
#define SE second
#define Vmin(a) *min_element((a).begin(), (a).end())
#define Vmax(a) *max_element((a).begin(), (a).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define FORR(i, a, b) for (int i = (b - 1); i >= (a); i--)
#define REPR(i, n) FORR(i, 0, n)
#define CFOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define CREP(i, n) CFOR(i, 0, n)
#define CFORR(i, a, b) for (int i = (b); i >= (a); i--)
#define CREPR(i, n) CFORR(i, 0, n)
#define BFOR(bit, a, b) for (int bit = (a); bit < (1 << (b)); ++bit)
#define BREP(bit, n) BFOR(bit, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = INT_MAX / 2;
const LL LINF = LLONG_MAX / 3;
const int RINF = INT_MIN / 2;
const LL RLINF = LLONG_MIN / 3;
const LL MOD = 1e9 + 7;
const LL MODD = 998244353;
const int MAX = 510000;

inline bool Eq(double a, double b) { return fabs(b - a) < EPS; }

// other
//-------------------------------------------
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

#define COUT(x) cout << (x) << endl
#define COUT2(x, y) cout << (x) << " " << (y) << endl
#define COUT3(x, y, z) cout << (x) << " " << (y) << " " << (z) << endl
#define PR(x) cout << (x)
#define ENDL cout << endl
#define SPACE cout << " "
#define BC(x) __builtin_popcountll(x)

VI dx = {1, 0, -1, 0, 1, 1, -1, -1};
VI dy = {0, 1, 0, -1, 1, -1, 1, -1};

LL Gcd(LL a, LL b) { return __gcd(a, b); }
LL Lcm(LL a, LL b) { return a / Gcd(a, b) * b; }

LL ModPow(LL A, LL N, LL M = MOD) {
  LL res = 1;
  while (N > 0) {
    if (N & 1)
      res = res * A % M;
    A = A * A % M;
    N >>= 1;
  }
  return res;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

struct UnionFind {

  VI par, siz;
  int cnt;

  UnionFind() {}

  UnionFind(int n) : par(n), siz(n, 1), cnt(n) { iota(ALL(par), 0); }

  void init(int n) {
    par.assign(n, 0);
    siz.assign(n, 1);
    iota(ALL(par), 0);
    cnt = n;
  }

  int find(int x) {
    if (par[x] == x) {
      return x;
    } else {
      return par[x] = find(par[x]);
    }
  }

  bool unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y)
      return false;
    cnt--;

    if (siz[x] < siz[y]) {
      swap(x, y);
    }
    siz[x] += siz[y];
    par[y] = x;
    return true;
  }

  bool same(int x, int y) { return find(x) == find(y); }

  int size(int x) { return siz[find(x)]; }
};

int main() {

  // cin.tie(0);
  // ios::sync_with_stdio(false);
  cout << fixed << setprecision(12);

  int N, Q;
  cin >> N >> Q;

  UnionFind uf(N);

  REP(i, Q) {
    int t, u, v;
    cin >> t >> u >> v;
    if (t == 0)
      uf.unite(u, v);
    else
      COUT(uf.same(u, v));
  }

  return 0;
}

Error: WA

Fixed submission:

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

// conversion
//------------------------------------------
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
template <class T> inline string toString(T x) {
  ostringstream sout;
  sout << x;
  return sout.str();
}

// math
//-------------------------------------------
template <class T> inline T sqr(T x) { return x * x; }

// typedef
//------------------------------------------
typedef long long LL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef vector<bool> VB;
typedef vector<VB> VVB;
typedef vector<double> VD;
typedef vector<VD> VVD;
typedef vector<string> VS;
typedef vector<VS> VVS;
typedef vector<char> VC;
typedef vector<VC> VVC;
typedef vector<PII> VPII;
typedef vector<PLL> VPLL;
typedef priority_queue<int> PQGI; // 大きい順
typedef priority_queue<int, VI, greater<int>> PQLI;
typedef priority_queue<PII> PQGP;
typedef priority_queue<PII, VPII, greater<PII>> PQLP;
// priority_queue<T,vector<T>,decltype(f)> pq{f};

// container util
//------------------------------------------
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define EB emplace_back
#define EF emplace_front
#define PB push_back
#define PF push_front
#define POB pop_back
#define POF pop_front
#define MP make_pair
#define SZ(a) int((a).size())
#define SQ(a) ((a) * (a))
#define EACH(i, c)                                                             \\
  for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define SORTR(c) sort((c).rbegin(), (c).rend())
#define LB lower_bound
#define UB upper_bound
#define NEXP next_permutation
#define FI first
#define SE second
#define Vmin(a) *min_element((a).begin(), (a).end())
#define Vmax(a) *max_element((a).begin(), (a).end())

// repetition
//------------------------------------------
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define REP(i, n) FOR(i, 0, n)
#define FORR(i, a, b) for (int i = (b - 1); i >= (a); i--)
#define REPR(i, n) FORR(i, 0, n)
#define CFOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define CREP(i, n) CFOR(i, 0, n)
#define CFORR(i, a, b) for (int i = (b); i >= (a); i--)
#define CREPR(i, n) CFORR(i, 0, n)
#define BFOR(bit, a, b) for (int bit = (a); bit < (1 << (b)); ++bit)
#define BREP(bit, n) BFOR(bit, 0, n)

// constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI = acos(-1.0);
const int INF = INT_MAX / 2;
const LL LINF = LLONG_MAX / 3;
const int RINF = INT_MIN / 2;
const LL RLINF = LLONG_MIN / 3;
const LL MOD = 1e9 + 7;
const LL MODD = 998244353;
const int MAX = 510000;

inline bool Eq(double a, double b) { return fabs(b - a) < EPS; }

// other
//-------------------------------------------
template <class T> bool chmax(T &a, const T &b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> bool chmin(T &a, const T &b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}

#define COUT(x) cout << (x) << endl
#define COUT2(x, y) cout << (x) << " " << (y) << endl
#define COUT3(x, y, z) cout << (x) << " " << (y) << " " << (z) << endl
#define PR(x) cout << (x)
#define ENDL cout << endl
#define SPACE cout << " "
#define BC(x) __builtin_popcountll(x)

VI dx = {1, 0, -1, 0, 1, 1, -1, -1};
VI dy = {0, 1, 0, -1, 1, -1, 1, -1};

LL Gcd(LL a, LL b) { return __gcd(a, b); }
LL Lcm(LL a, LL b) { return a / Gcd(a, b) * b; }

LL ModPow(LL A, LL N, LL M = MOD) {
  LL res = 1;
  while (N > 0) {
    if (N & 1)
      res = res * A % M;
    A = A * A % M;
    N >>= 1;
  }
  return res;
}

template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) {
  os << p.first << " " << p.second;
  return os;
}

template <typename T> istream &operator>>(istream &is, vector<T> &v) {
  for (T &in : v)
    is >> in;
  return is;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &v) {
  for (int i = 0; i < (int)v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template <typename T> vector<T> make_v(size_t a, T b) {
  return vector<T>(a, b);
}
template <typename... Ts> auto make_v(size_t a, Ts... ts) {
  return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

struct UnionFind {

  VI par, siz;
  int cnt;

  UnionFind() {}

  UnionFind(int n) : par(n), siz(n, 1), cnt(n) { iota(ALL(par), 0); }

  void init(int n) {
    par.assign(n, 0);
    siz.assign(n, 1);
    iota(ALL(par), 0);
    cnt = n;
  }

  int find(int x) {
    if (par[x] == x) {
      return x;
    } else {
      return par[x] = find(par[x]);
    }
  }

  bool unite(int x, int y) {
    x = find(x);
    y = find(y);
    if (x == y)
      return false;
    cnt--;

    if (siz[x] < siz[y]) {
      swap(x, y);
    }
    siz[x] += siz[y];
    par[y] = x;
    return true;
  }

  bool same(int x, int y) { return find(x) == find(y); }

  int size(int x) { return siz[find(x)]; }
};

int main() {

  // cin.tie(0);
  // ios::sync_with_stdio(false);
  cout << fixed << setprecision(12);

  int N, Q;
  cin >> N >> Q;

  UnionFind uf(N);

  REP(i, Q) {
    int t, u, v;
    cin >> t >> u >> v;
    u--;
    v--;
    if (t == 0)
      uf.unite(u, v);
    else
      COUT(uf.same(u, v));
  }

  return 0;
}