Language: C++

#include <iostream> // cin, cout, cerr, clog
#include <algorithm> // minmax, sort, swap
#include <numeric> // iota, gcd, lcm 
#include <cstdio> // printf, scanf
#include <climits> // INT_MIN, LLONG_MIN
#include <cmath> // long, trig, pow
#include <vector> // vectors
#include <string> // string
#include <queue> // queue
#include <stack> // stack
#include <map> // key-value pairs sorted by keys
#include <unordered_map> // hashed by keys
#define _for(i,n) for(int i = 0; i < n; i++)

typedef long long ll; // at least int64 > 9*10^18
typedef unsigned long long ull; // at least uint64

bool went[100000]={};

void dfs(int i,std::vector<std::vector<int>> &connected) {
  went[i] = 1;
  _for(j,connected[i].size()) {
    if(went[connected[i][j]]==0)dfs(connected[i][j],connected);
  }
}

int main() {
  int n,m;
  std::cin >> n >> m;
  int x[n][2];
  int z[n];
  std::vector<std::vector<int>> connected(n,std::vector<int>());
  _for(i,m) {
    std::cin >> x[i][0] >> x[i][1] >> z[i];
    _for(j,2) x[i][j]--;
    connected[x[i][0]].emplace_back(x[i][1]);
    connected[x[i][1]].emplace_back(x[i][0]);
  }
  int count = 0;

  _for(i,n) {
    if(went[i]==0) {
      count ++;
      std::queue<int> que;
      que.emplace(i);
      while(que.size()) {
        _for(k,connected[que.front].size()) {
          if(went[connected[que.front][k]]==0){
            que.emplace(connected[que.front][k]);
            went[connected[que.front][k]] = 1;
          }
        }
        que.pop();
      }
    }
  }
  std::cout << count << std::endl;

  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:47:25: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and '<unresolved overloaded function type>')
   47 |         _for(k,connected[que.front].size()) {
      |                         ^
a.cc:13:38: note: in definition of macro '_for'
   13 | #define _for(i,n) for(int i = 0; i < n; i++)
      |                                      ^
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:7:
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:48:28: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and '<unresolved overloaded function type>')
   48 |           if(went[connected[que.front][k]]==0){
      |                            ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:49:34: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and '<unresolved overloaded function type>')
   49 |             que.emplace(connected[que.front][k]);
      |                                  ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
a.cc:50:27: error: no match for 'operator[]' (operand types are 'std::vector<std::vector<int> >' and '<unresolved overloaded function type>')
   50 |             went[connected[que.front][k]] = 1;
      |                           ^
/usr/include/c++/14/bits/stl_vector.h:1128:7: note: candidate: 'std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::operator[](size_type) [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; reference = std::vector<int>&; size_type = long unsigned int]'
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1128:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1128 |       operator[](size_type __n) _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~
/usr/include/c++/14/bits/stl_vector.h:1147:7: note: candidate: 'std::vector<_Tp, _Alloc>::const_reference std::vector<_Tp, _Alloc>::operator[](size_type) const [with _Tp = std::vector<int>; _Alloc = std::allocator<std::vector<int> >; const_reference = const std::vector<int>&; size_type = long unsigned int]'
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |       ^~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:1147:28: note:   no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'}
 1147 |       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
      |                  ~~~~~~~~~~^~~