Compilare: main.cpp: In function 'void solve1(const std::vector<std::vector<int> >&, int, int)': main.cpp:19:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 19 | for (int i = 0; i < mat.size(); i++) { | ~~^~~~~~~~~~~~ main.cpp:20:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | for (int j = 0; j < mat[i].size(); j++) { | ~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:55:32: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare] 55 | for (unsigned int i = 0; i < lines; i++) { | ~~^~~~~~~ main.cpp:56:36: warning: comparison of integer expressions of different signedness: 'unsigned int' and 'int' [-Wsign-compare] 56 | for (unsigned int j = 0; j < columns; j++) { | ~~^~~~~~~~~