Compilare: main.cpp: In function 'void solve1(std::vector<std::vector<int> >&)': main.cpp:65:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 65 | for (int i = 0; i < mat.size(); i++) { | ~~^~~~~~~~~~~~ main.cpp:66:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 66 | for (int j = 0; j < mat[i].size(); j++) { | ~~^~~~~~~~~~~~~~~ main.cpp: In function 'bool checkMatrix(const std::vector<std::vector<int> >&, int)': main.cpp:83:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 83 | for (int i = 0; i < mat.size(); i++) { | ~~^~~~~~~~~~~~ main.cpp:84:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 84 | for (int j = 0; j < mat[i].size(); j++) { | ~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:129:32: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare] 129 | for (unsigned int i = 0; i < lines; i++) { | ~~^~~~~~~ main.cpp:130:36: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare] 130 | for (unsigned int j = 0; j < columns; j++) { | ~~^~~~~~~~~