Problem p02364 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

#define TemplateVersion "3.2.0"
// Useful Marcos
//====================START=====================
// Compile use C++11 and above
#ifdef LOCAL
#define debug(args...)                                                         \
  {                                                                            \
    string _s = #args;                                                         \
    replace(_s.begin(), _s.end(), ',', ' ');                                   \
    stringstream _ss(_s);                                                      \
    istream_iterator<string> _it(_ss);                                         \
    err(_it, args);                                                            \
  }
void err(istream_iterator<string> it) {}
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  err(++it, args...);
}
#define MSG cout << "Finished" << endl
#else
#define debug(args...)
#define MSG
#endif
#if __cplusplus >= 201703L
template <typename... Args> void readln(Args &...args) { ((cin >> args), ...); }
template <typename... Args> void writeln(Args... args) {
  ((cout << args << " "), ...);
  cout << endl;
}
#elif __cplusplus >= 201103L
void readln() {}
template <typename T, typename... Args> void readln(T &a, Args &...args) {
  cin >> a;
  readln(args...);
}
void writeln() { cout << endl; }
template <typename T, typename... Args> void writeln(T a, Args... args) {
  cout << a << " ";
  writeln(args...);
}
#endif
#if __cplusplus >= 201103L
#define FOR(_i, _begin, _end) for (auto _i = _begin; _i < _end; _i++)
#define FORR(_i, _begin, _end) for (auto _i = _begin; _i > _end; _i--)
#else
#define FOR(_i, _begin, _end) for (int _i = (int)_begin; _i < (int)_end; _i++)
#define FORR(_i, _begin, _end) for (int _i = (int)_begin; _i > (int)_end; _i--)
#define nullptr NULL
#endif
#if __cplusplus >= 201103L
#define VIS(_kind, _name, _size)                                               \
  vector<_kind> _name(_size);                                                  \
  for (auto &i : _name)                                                        \
    cin >> i;
#else
#define VIS(_kind, _name, _size)                                               \
  vector<_kind> _name;                                                         \
  _name.resize(_size);                                                         \
  for (int i = 0; i < _size; i++)                                              \
    cin >> _name[i];
#endif
// alias
#define mp make_pair
#define pb push_back
#define eb emplace_back
// Swap max/min
template <typename T> bool smax(T &a, const T &b) {
  if (a > b)
    return false;
  a = b;
  return true;
}
template <typename T> bool smin(T &a, const T &b) {
  if (a < b)
    return false;
  a = b;
  return true;
}
// ceil divide
template <typename T> T cd(T a, T b) { return (a + b - 1) / b; }
// min exchange
template <typename T> bool se(T &a, T &b) {
  if (a < b)
    return false;
  swap(a, b);
  return true;
}
// A better MAX choice
const int INF = 0x3f3f3f3f;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef set<int> si;
typedef vector<string> cb;
//====================END=====================

// Constants here
const int MAXN = 10010;
const int MAXM = 100010;
int F[MAXN];
struct Edge {
  int u, v, w;
} edge[MAXN];
int tol;
void addedge(int u, int v, int w) {
  edge[tol].u = u;
  edge[tol].v = v;
  edge[tol++].w = w;
}
bool cmp(Edge a, Edge b) { return a.w < b.w; }
int find(int x) {
  if (F[x] == -1)
    return x;
  else
    return F[x] = find(F[x]);
}
int Kruskal(int n) {
  memset(F, -1, sizeof(F));
  sort(edge, edge + tol, cmp);
  int cnt = 0;
  int ans = 0;
  for (int i = 0; i < tol; i++) {
    int u = edge[i].u;
    int v = edge[i].v;
    int w = edge[i].w;
    int t1 = find(u);
    int t2 = find(v);
    if (t1 != t2) {
      ans += w;
      F[t1] = t2;
      cnt++;
    }
    if (cnt == n - 1)
      break;
  }
  if (cnt < n - 1)
    return -1;
  else
    return ans;
}

// Pre-Build Function
inline void build() {}

// Actual Solver
inline void solve() {
  int n, m;
  int u, v, w;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> u >> v >> w;
    addedge(u, v, w);
  }
  cout << Kruskal(n) << "\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);

#ifdef LOCAL
  clock_t _begin = clock();
#endif

  build();
  solve();

#ifdef LOCAL
  cerr << "Time elapsed: " << (double)(clock() - _begin) * 1000 / CLOCKS_PER_SEC
       << "ms." << endl;
#endif

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

#define TemplateVersion "3.2.0"
// Useful Marcos
//====================START=====================
// Compile use C++11 and above
#ifdef LOCAL
#define debug(args...)                                                         \
  {                                                                            \
    string _s = #args;                                                         \
    replace(_s.begin(), _s.end(), ',', ' ');                                   \
    stringstream _ss(_s);                                                      \
    istream_iterator<string> _it(_ss);                                         \
    err(_it, args);                                                            \
  }
void err(istream_iterator<string> it) {}
template <typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  err(++it, args...);
}
#define MSG cout << "Finished" << endl
#else
#define debug(args...)
#define MSG
#endif
#if __cplusplus >= 201703L
template <typename... Args> void readln(Args &...args) { ((cin >> args), ...); }
template <typename... Args> void writeln(Args... args) {
  ((cout << args << " "), ...);
  cout << endl;
}
#elif __cplusplus >= 201103L
void readln() {}
template <typename T, typename... Args> void readln(T &a, Args &...args) {
  cin >> a;
  readln(args...);
}
void writeln() { cout << endl; }
template <typename T, typename... Args> void writeln(T a, Args... args) {
  cout << a << " ";
  writeln(args...);
}
#endif
#if __cplusplus >= 201103L
#define FOR(_i, _begin, _end) for (auto _i = _begin; _i < _end; _i++)
#define FORR(_i, _begin, _end) for (auto _i = _begin; _i > _end; _i--)
#else
#define FOR(_i, _begin, _end) for (int _i = (int)_begin; _i < (int)_end; _i++)
#define FORR(_i, _begin, _end) for (int _i = (int)_begin; _i > (int)_end; _i--)
#define nullptr NULL
#endif
#if __cplusplus >= 201103L
#define VIS(_kind, _name, _size)                                               \
  vector<_kind> _name(_size);                                                  \
  for (auto &i : _name)                                                        \
    cin >> i;
#else
#define VIS(_kind, _name, _size)                                               \
  vector<_kind> _name;                                                         \
  _name.resize(_size);                                                         \
  for (int i = 0; i < _size; i++)                                              \
    cin >> _name[i];
#endif
// alias
#define mp make_pair
#define pb push_back
#define eb emplace_back
// Swap max/min
template <typename T> bool smax(T &a, const T &b) {
  if (a > b)
    return false;
  a = b;
  return true;
}
template <typename T> bool smin(T &a, const T &b) {
  if (a < b)
    return false;
  a = b;
  return true;
}
// ceil divide
template <typename T> T cd(T a, T b) { return (a + b - 1) / b; }
// min exchange
template <typename T> bool se(T &a, T &b) {
  if (a < b)
    return false;
  swap(a, b);
  return true;
}
// A better MAX choice
const int INF = 0x3f3f3f3f;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef set<int> si;
typedef vector<string> cb;
//====================END=====================

// Constants here
const int MAXN = 10010;
const int MAXM = 100010;
int F[MAXN];
struct Edge {
  int u, v, w;
} edge[MAXM];
int tol;
void addedge(int u, int v, int w) {
  edge[tol].u = u;
  edge[tol].v = v;
  edge[tol++].w = w;
}
bool cmp(Edge a, Edge b) { return a.w < b.w; }
int find(int x) {
  if (F[x] == -1)
    return x;
  else
    return F[x] = find(F[x]);
}
int Kruskal(int n) {
  memset(F, -1, sizeof(F));
  sort(edge, edge + tol, cmp);
  int cnt = 0;
  int ans = 0;
  for (int i = 0; i < tol; i++) {
    int u = edge[i].u;
    int v = edge[i].v;
    int w = edge[i].w;
    int t1 = find(u);
    int t2 = find(v);
    if (t1 != t2) {
      ans += w;
      F[t1] = t2;
      cnt++;
    }
    if (cnt == n - 1)
      break;
  }
  if (cnt < n - 1)
    return -1;
  else
    return ans;
}

// Pre-Build Function
inline void build() {}

// Actual Solver
inline void solve() {
  int n, m;
  int u, v, w;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    cin >> u >> v >> w;
    addedge(u, v, w);
  }
  cout << Kruskal(n) << "\n";
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);

#ifdef LOCAL
  clock_t _begin = clock();
#endif

  build();
  solve();

#ifdef LOCAL
  cerr << "Time elapsed: " << (double)(clock() - _begin) * 1000 / CLOCKS_PER_SEC
       << "ms." << endl;
#endif

  return 0;
}