Compilare: main.cpp: In function 'bool solve(double)': main.cpp:48:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<elem>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 48 | for (int j=0; j<v[i].size(); j++) | ~^~~~~~~~~~~~ main.cpp:65:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<elem>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 65 | for (int j=0; j<v[i].size(); j++) | ~^~~~~~~~~~~~