Compilare: user.cpp: In constructor ‘state_machine::tree::tree()’: user.cpp:30:23: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_words = NULL; ^ user.cpp:32:26: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_children = NULL; ^ user.cpp:33:29: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] cnt_occurrences = NULL; ^ user.cpp: In member function ‘void state_machine::insert_word(state_machine::tree*, char*)’: user.cpp:45:24: warning: NULL used in arithmetic [-Wpointer-arith] if( *String == NULL ) { ^ user.cpp: In member function ‘void state_machine::build_occurrences(state_machine::tree*, char*)’: user.cpp:92:24: warning: NULL used in arithmetic [-Wpointer-arith] if( *String == NULL ) ^ user.cpp: In member function ‘void state_machine::build_partial_sum(state_machine::tree*)’: user.cpp:109:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < Node -> front_node.size(); i ++ ) { ^ user.cpp: In member function ‘int state_machine::count_occurrences(state_machine::tree*, char*)’: user.cpp:119:24: warning: NULL used in arithmetic [-Wpointer-arith] if( *String == NULL ) ^ user.cpp: In function ‘int main()’: user.cpp:166:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "abc2.in" , "r", stdin ); ^ user.cpp:167:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "abc2.out", "w", stdout ); ^ user.cpp:169:36: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets( String, 1 << 24, stdin ); String[strlen( String ) - 1] = 0; ^