Compilare: user.cpp: In function ‘int main()’: user.cpp:42:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v.size(); j++) { ^ user.cpp:46:28: warning: NULL used in arithmetic [-Wpointer-arith] if(b[index] == NULL){ ^ user.cpp:52:24: warning: NULL used in arithmetic [-Wpointer-arith] if(b[index] == NULL){ ^ user.cpp:33:9: warning: unused variable ‘N’ [-Wunused-variable] int N, i; ^ user.cpp:33:12: warning: unused variable ‘i’ [-Wunused-variable] int N, i; ^