Compilare: user.cpp: In function ‘int main()’: user.cpp:22:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] { for (i=0; i<A[k].size(); ++i) ^ user.cpp:23:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=i+1; j<A[k].size(); ++j) ^