Compilare: main.cpp: In function 'int main()': main.cpp:54:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 54 | for (i = 0; i < sol.size(); i++) | ~~^~~~~~~~~~~~ main.cpp:57:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 57 | for (j = 0; j < sol[i].size(); j++) | ~~^~~~~~~~~~~~~~~