Borderou de evaluare (job #1014)

Eroare de compilare: user.cpp:3:12: error: variable ‘std::ifstream in’ has initializer but incomplete type user.cpp:4:13: error: variable ‘std::ofstream out’ has initializer but incomplete type user.cpp: In function ‘bool valid(int)’: user.cpp:25:1: error: expected primary-expression before ‘}’ token user.cpp:25:1: error: expected ‘;’ before ‘}’ token user.cpp:25:1: warning: no return statement in function returning non-void [-Wreturn-type] user.cpp: In function ‘void back()’: user.cpp:42:16: error: ‘succesor’ was not declared in this scope