Compilare: In file included from /usr/include/c++/4.2/backward/iostream.h:31, from user.cpp:2: /usr/include/c++/4.2/backward/backward_warning.h:32:2: warning: #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the <X> header for the <X.h> header for C++ includes, or <iostream> instead of the deprecated header <iostream.h>. To disable this warning use -Wno-deprecated. user.cpp: In function 'int search_node(int)': user.cpp:48: warning: NULL used in arithmetic user.cpp:51: warning: control reaches end of non-void function user.cpp: In function 'int delete_node(int)': user.cpp:39: warning: control reaches end of non-void function user.cpp: In function 'int add_node(int)': user.cpp:21: warning: control reaches end of non-void function