src.cpp: In function 'void nhap()':
src.cpp:13:13: error: request for member 'push_back' in 'a.std::vector<_Tp, _Alloc>::operator[]<int, std::allocator<int> >(((std::vector<int>::size_type)x))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}'
a[x].push_back(y);
^
src.cpp:14:13: error: request for member 'push_back' in 'a.std::vector<_Tp, _Alloc>::operator[]<int, std::allocator<int> >(((std::vector<int>::size_type)y))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}'
a[y].push_back(x);
^
src.cpp:16:29: error: request for member 'push_back' in 'a.std::vector<_Tp, _Alloc>::operator[]<int, std::allocator<int> >(((std::vector<int>::size_type)i))', which is of non-class type '__gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}'
for (i=0;i<=n;i++) a[i].push_back(0);
^
src.cpp: In function 'void bfs(long long int)':
src.cpp:27:31: error: invalid types '__gnu_cxx::__alloc_traits<std::allocator<int> >::value_type {aka int}[int]' for array subscript
for (i=0; int v=a[u][i];i++)
^