sortbooks.cpp: In function 'int main()':
sortbooks.cpp:42:3: error: 'v1' was not declared in this scope; did you mean '__pstl::execution::v1'?
42 | v1.clear();
| ^~
| __pstl::execution::v1
In file included from /usr/include/c++/10/pstl/glue_algorithm_defs.h:15,
from /usr/include/c++/10/algorithm:74,
from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:65,
from sortbooks.cpp:1:
/usr/include/c++/10/pstl/execution_defs.h:19:18: note: '__pstl::execution::v1' declared here
19 | inline namespace v1
| ^~