In file included from /usr/include/c++/7/algorithm:62:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:65, from Main.cc:1: /usr/include/c++/7/bits/stl_algo.h: In instantiation of ‘void std::shuffle(_RAIter, _RAIter, _UGenerator&&) [with _RAIter = nd*; _UGenerator = unsigned int&]’: Main.cc:33:27: required from here /usr/include/c++/7/bits/stl_algo.h:3813:2: error: ‘std::remove_reference::type {aka unsigned int}’ is not a class, struct, or union type __uc_type; ^~~~~~~~~ /usr/include/c++/7/bits/stl_algo.h:3841:37: error: ‘std::remove_reference::type {aka unsigned int}’ is not a class, struct, or union type const pair<__uc_type, __uc_type> __pospos = ^~~~~~~~ /usr/include/c++/7/bits/stl_algo.h:3841:37: error: ‘std::remove_reference::type {aka unsigned int}’ is not a class, struct, or union type