Compilare: user.cpp: In function ‘void precalcV()’: user.cpp:67:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < X[i].size(); j++) ^ user.cpp:74:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < X2[i].size(); j++) ^ user.cpp:96:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < X2[i].size(); j++) ^ user.cpp:103:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < X[i].size(); j++) ^