Compilare: user.cpp: In function ‘int main()’: user.cpp:21:11: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] q[m+1]=NULL; ^ user.cpp:41:16: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] z[lg-k]=NULL; ^ user.cpp:43:18: warning: NULL used in arithmetic [-Wpointer-arith] if(z[0]==NULL) ^ user.cpp:48:31: warning: NULL used in arithmetic [-Wpointer-arith] for(int i=0;q[i]!=NULL;i++) ^