Compilare: main.cpp: In function 'void back(int, int, std::vector<int>, int)': main.cpp:10:20: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare] 10 | if (ans.size() == k) { | ~~~~~~~~~~~^~~~ main.cpp: In function 'int main()': main.cpp:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 31 | for (int i = 0; i < sol.size(); i++) { | ~~^~~~~~~~~~~~ main.cpp:32:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 32 | for (int j = 0; j < sol[i].size(); j++) { | ~~^~~~~~~~~~~~~~~