Main.cc: In function ‘int main()’: Main.cc:53:68: error: wrong number of template arguments (0, should be 1) arr.emplace_back(accumulate(arr.begin(), arr.end(), 0, bit_xor<>())); ^ In file included from /usr/include/c++/7/functional:49:0, from Main.cc:1: /usr/include/c++/7/bits/stl_function.h:635:12: note: provided for ‘template struct std::bit_xor’ struct bit_xor : public binary_function<_Tp, _Tp, _Tp> ^~~~~~~ Main.cc:54:77: error: wrong number of template arguments (0, should be 1) target.emplace_back(accumulate(target.begin(), target.end(), 0, bit_xor<>())); ^ In file included from /usr/include/c++/7/functional:49:0, from Main.cc:1: /usr/include/c++/7/bits/stl_function.h:635:12: note: provided for ‘template struct std::bit_xor’ struct bit_xor : public binary_function<_Tp, _Tp, _Tp> ^~~~~~~ Main.cc:74:22: warning: decomposition declaration only available with -std=c++1z or -std=gnu++1z for (const auto& [u, _] : G) { ^ Main.cc:74:27: warning: unused variable ‘_’ [-Wunused-variable] for (const auto& [u, _] : G) { ^