Compilare: user.cpp: In function ‘int main()’: user.cpp:68:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( j = 0 ; j < grp[i].size() - 1 ; j++ ) ^ user.cpp:70:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( k = j + 1 ; k < grp[i].size() ; k++ ) ^