Compilare: main.cpp: In function 'void afis(std::vector<std::vector<bool> >&)': main.cpp:20:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<bool> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | for(int i = 1; i <= mat.size() - 1; ++i) | ~~^~~~~~~~~~~~~~~~~ main.cpp:22:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<bool>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 22 | for(int j = 1; j <= mat[i].size() - 1; ++j) | ~~^~~~~~~~~~~~~~~~~~~~