Compilare: main.cpp: In member function 'void skip_list::insert_node(int)': main.cpp:347:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node*>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 347 | for (int i = 1; i < levels.size(); i++) | ~~^~~~~~~~~~~~~~~ main.cpp:363:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<node*>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 363 | if (level >= levels.size()) | ~~~~~~^~~~~~~~~~~~~~~~