Language: C++

#include <iostream>
#include <vector>
#include <map>
#include <regex>
#include <tuple>
#include <regex>
#include <string>
#include <type_traits>
#include <functional>
#include <memory>
#include <sstream>
#include <algorithm>
#include <thread>
int main() {
  int N ,sum;
  sum = 0;
  cin >> N;
  vector<int> vec(N);
  
    for (int i = 0; i < N; i++) {
      cin >> vec.at(i);
    }
  
  sort(vec.begin(), vec.end());
  reverse(vec.begin(), vec.end());
    for (int i = 0; i < N; i += 2){
      cout << sum << endl;
      sum +=vec.at(i);
      cout << sum << endl;
    }
  cout << sum << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:17:3: error: 'cin' was not declared in this scope; did you mean 'std::cin'?
   17 |   cin >> N;
      |   ^~~
      |   std::cin
In file included from a.cc:1:
/usr/include/c++/14/iostream:62:18: note: 'std::cin' declared here
   62 |   extern istream cin;           ///< Linked to standard input
      |                  ^~~
a.cc:18:3: error: 'vector' was not declared in this scope
   18 |   vector<int> vec(N);
      |   ^~~~~~
a.cc:18:3: note: suggested alternatives:
In file included from /usr/include/c++/14/vector:66,
                 from a.cc:2:
/usr/include/c++/14/bits/stl_vector.h:428:11: note:   'std::vector'
  428 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
/usr/include/c++/14/vector:93:13: note:   'std::pmr::vector'
   93 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
a.cc:18:10: error: expected primary-expression before 'int'
   18 |   vector<int> vec(N);
      |          ^~~
a.cc:21:14: error: 'vec' was not declared in this scope
   21 |       cin >> vec.at(i);
      |              ^~~
a.cc:24:8: error: 'vec' was not declared in this scope
   24 |   sort(vec.begin(), vec.end());
      |        ^~~
a.cc:24:3: error: 'sort' was not declared in this scope; did you mean 'std::sort'?
   24 |   sort(vec.begin(), vec.end());
      |   ^~~~
      |   std::sort
In file included from /usr/include/c++/14/algorithm:86,
                 from a.cc:12:
/usr/include/c++/14/pstl/glue_algorithm_defs.h:296:1: note: 'std::sort' declared here
  296 | sort(_ExecutionPolicy&& __exec, _RandomAccessIterator __first, _RandomAccessIterator __last);
      | ^~~~
a.cc:25:3: error: 'reverse' was not declared in this scope; did you mean 'std::reverse'?
   25 |   reverse(vec.begin(), vec.end());
      |   ^~~~~~~
      |   std::reverse
/usr/include/c++/14/pstl/glue_algorithm_defs.h:249:1: note: 'std::reverse' declared here
  249 | reverse(_ExecutionPolicy&& __exec, _BidirectionalIterator __first, _BidirectionalIterator __last);
      | ^~~~~~~
a.cc:27:7: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   27 |       cout << sum << endl;
      |       ^~~~
      |       std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:27:22: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   27 |       cout << sum << endl;
      |                      ^~~~
      |                      std::endl
In file included from /usr/include/c++/14/iostream:41:
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~
a.cc:31:3: error: 'cout' was not declared in this scope; did you mean 'std::cout'?
   31 |   cout << sum << endl;
      |   ^~~~
      |   std::cout
/usr/include/c++/14/iostream:63:18: note: 'std::cout' declared here
   63 |   extern ostream cout;          ///< Linked to standard output
      |                  ^~~~
a.cc:31:18: error: 'endl' was not declared in this scope; did you mean 'std::endl'?
   31 |   cout << sum << endl;
      |                  ^~~~
      |                  std::endl
/usr/include/c++/14/ostream:744:5: note: 'std::endl' declared here
  744 |     endl(basic_ostream<_CharT, _Traits>& __os)
      |     ^~~~