Language: C++

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ll long long
vector<bool> seen;
void dfs(vector<vector<ll,ll>> &G, int v){
  seen[v]=true;
  for(ll nv: G[v]){
    if(seen[nv]){
      continue;
    }
    dfs(G,nv);
  }
}
int main(){
  ll n,q;
  cin  >> n >> q;
  vector<vector<ll,ll>> G(n);
  rep(i,n){
    ll a,b;
    cin >> a >> b;
    a--;
    b--;
    G(a).push_back(b);
    G(b).push_back(a);
  }
  seen.assign(n,false);
  dfs(G,0);

Compiler output:
In file included from /usr/include/c++/14/vector:66,
                 from /usr/include/c++/14/functional:64,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_vector.h: In instantiation of 'struct std::_Vector_base<long long int, long long int>':
/usr/include/c++/14/bits/stl_vector.h:428:11:   required from 'class std::vector<long long int, long long int>'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/stl_vector.h:87:28: error: 'long long int' is not a class, struct, or union type
   87 |         rebind<_Tp>::other _Tp_alloc_type;
      |                            ^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:89:9: error: 'long long int' is not a class, struct, or union type
   89 |         pointer;
      |         ^~~~~~~
/usr/include/c++/14/bits/stl_vector.h: In instantiation of 'class std::vector<long long int, long long int>':
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/stl_vector.h:518:20: error: '_M_allocate' has not been declared in 'std::vector<long long int, long long int>::_Base'
  518 |       using _Base::_M_allocate;
      |                    ^~~~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:519:20: error: '_M_deallocate' has not been declared in 'std::vector<long long int, long long int>::_Base'
  519 |       using _Base::_M_deallocate;
      |                    ^~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_vector.h:521:20: error: '_M_get_Tp_allocator' has not been declared in 'std::vector<long long int, long long int>::_Base'
  521 |       using _Base::_M_get_Tp_allocator;
      |                    ^~~~~~~~~~~~~~~~~~~
a.cc: In function 'void dfs(std::vector<std::vector<long long int, long long int> >&, int)':
a.cc:8:17: error: no matching function for call to 'begin(std::vector<long long int, long long int>&)'
    8 |   for(ll nv: G[v]){
      |                 ^
In file included from /usr/include/c++/14/bits/algorithmfwd.h:39,
                 from /usr/include/c++/14/bits/stl_algo.h:59,
                 from /usr/include/c++/14/algorithm:61,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/initializer_list:88:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::begin(initializer_list<_Tp>)'
   88 |     begin(initializer_list<_Tp> __ils) noexcept
      |     ^~~~~
/usr/include/c++/14/initializer_list:88:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'std::initializer_list<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/range_access.h:52:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&)'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:52:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(_Container&) [with _Container = std::vector<long long int, long long int>]':
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:52:50: error: 'class std::vector<long long int, long long int>' has no member named 'begin'
   52 |     begin(_Container& __cont) -> decltype(__cont.begin())
      |                                           ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&)'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:63:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.begin()) std::begin(const _Container&) [with _Container = std::vector<long long int, long long int>]':
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:63:56: error: 'const class std::vector<long long int, long long int>' has no member named 'begin'
   63 |     begin(const _Container& __cont) -> decltype(__cont.begin())
      |                                                 ~~~~~~~^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::begin(_Tp (&)[_Nm])'
   95 |     begin(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~~~
/usr/include/c++/14/bits/range_access.h:95:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   mismatched types '_Tp [_Nm]' and 'std::vector<long long int, long long int>'
    8 |   for(ll nv: G[v]){
      |                 ^
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/valarray:1227:5: note: candidate: 'template<class _Tp> _Tp* std::begin(valarray<_Tp>&)'
 1227 |     begin(valarray<_Tp>& __va) noexcept
      |     ^~~~~
/usr/include/c++/14/valarray:1227:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'std::valarray<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/valarray:1238:5: note: candidate: 'template<class _Tp> const _Tp* std::begin(const valarray<_Tp>&)'
 1238 |     begin(const valarray<_Tp>& __va) noexcept
      |     ^~~~~
/usr/include/c++/14/valarray:1238:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'const std::valarray<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
a.cc:8:17: error: no matching function for call to 'end(std::vector<long long int, long long int>&)'
/usr/include/c++/14/initializer_list:99:5: note: candidate: 'template<class _Tp> constexpr const _Tp* std::end(initializer_list<_Tp>)'
   99 |     end(initializer_list<_Tp> __ils) noexcept
      |     ^~~
/usr/include/c++/14/initializer_list:99:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'std::initializer_list<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:74:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&)'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:74:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(_Container&) [with _Container = std::vector<long long int, long long int>]':
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:74:48: error: 'class std::vector<long long int, long long int>' has no member named 'end'
   74 |     end(_Container& __cont) -> decltype(__cont.end())
      |                                         ~~~~~~~^~~
/usr/include/c++/14/bits/range_access.h:85:5: note: candidate: 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&)'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |     ^~~
/usr/include/c++/14/bits/range_access.h:85:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/range_access.h: In substitution of 'template<class _Container> constexpr decltype (__cont.end()) std::end(const _Container&) [with _Container = std::vector<long long int, long long int>]':
a.cc:8:17:   required from here
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/bits/range_access.h:85:54: error: 'const class std::vector<long long int, long long int>' has no member named 'end'
   85 |     end(const _Container& __cont) -> decltype(__cont.end())
      |                                               ~~~~~~~^~~
/usr/include/c++/14/bits/range_access.h:106:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::end(_Tp (&)[_Nm])'
  106 |     end(_Tp (&__arr)[_Nm]) noexcept
      |     ^~~
/usr/include/c++/14/bits/range_access.h:106:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   mismatched types '_Tp [_Nm]' and 'std::vector<long long int, long long int>'
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/valarray:1249:5: note: candidate: 'template<class _Tp> _Tp* std::end(valarray<_Tp>&)'
 1249 |     end(valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1249:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'std::valarray<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
/usr/include/c++/14/valarray:1265:5: note: candidate: 'template<class _Tp> const _Tp* std::end(const valarray<_Tp>&)'
 1265 |     end(const valarray<_Tp>& __va) noexcept
      |     ^~~
/usr/include/c++/14/valarray:1265:5: note:   template argument deduction/substitution failed:
a.cc:8:17: note:   'std::vector<long long int, long long int>' is not derived from 'const std::valarray<_Tp>'
    8 |   for(ll nv: G[v]){
      |                 ^
a.cc: In function 'int main()':
a.cc:24:6: error: no match for call to '(std::vector<std::vector<long long int, long long int> >) (long long int&)'
   24 |     G(a).push_back(b);
      |     ~^~~
a.cc:25:6: error: no match for call to '(std::vector<std::vector<long