shoes.cpp:4:23: error: 'long long int count_swaps' redeclared as different kind of entity
    4 | long long count_swaps(vector<int> S)
      |                       ^~~~~~
In file included from shoes.cpp:1:
shoes.h:7:11: note: previous declaration 'long long int count_swaps(std::vector<int>)'
    7 | long long count_swaps(std::vector<int> S);
      |           ^~~~~~~~~~~
shoes.cpp:4:23: error: 'vector' was not declared in this scope
    4 | long long count_swaps(vector<int> S)
      |                       ^~~~~~
shoes.cpp:4:23: note: suggested alternatives:
In file included from /usr/include/c++/9/vector:67,
                 from shoes.h:5,
                 from shoes.cpp:1:
/usr/include/c++/9/bits/stl_vector.h:386:11: note:   'std::vector'
  386 |     class vector : protected _Vector_base<_Tp, _Alloc>
      |           ^~~~~~
In file included from shoes.h:5,
                 from shoes.cpp:1:
/usr/include/c++/9/vector:90:13: note:   'std::pmr::vector'
   90 |       using vector = std::vector<_Tp, polymorphic_allocator<_Tp>>;
      |             ^~~~~~
shoes.cpp:4:30: error: expected primary-expression before 'int'
    4 | long long count_swaps(vector<int> S)
      |                              ^~~