Compilare: user.cpp: In function ‘int main()’: user.cpp:105:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < output.size(); i++) { ^ user.cpp:107:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < output[i]->size(); j++) { ^