Compilare: user.cpp: In function ‘int main()’: user.cpp:20:18: warning: converting to non-pointer type ‘unsigned int’ from NULL [-Wconversion-null] prim = ultim = NULL; ^ user.cpp:21:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 1 ; i <= NMAX ; i ++ ) ^ user.cpp:24:22: warning: NULL used in arithmetic [-Wpointer-arith] if ( prim == NULL ) ^ user.cpp:29:28: warning: converting to non-pointer type ‘unsigned int’ from NULL [-Wconversion-null] lista[ p ].urm = NULL; ^ user.cpp:43:28: warning: converting to non-pointer type ‘unsigned int’ from NULL [-Wconversion-null] lista[ i ].urm = NULL; ^