Compilare: main.cpp: In function 'int main()': main.cpp:31:39: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<elem>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 31 | for( j = 0; j < v[i].size(); j++ ){ | ~~^~~~~~~~~~~~~ main.cpp:47:47: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<elem>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 47 | for( i = 0; i < v[x].size(); i++ ){ | ~~^~~~~~~~~~~~~