I changed it, but it still doesn't work...
Student.obj : error LNK2001: unresolved external symbol "public: void __thiscall Student::Quicksort(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > * const,int)" (?Quicksort@Student@@QAEXQAV?$basic_string@DU?$
char_traits@D@std@@V?$allocator@D@2@@std@@H@Z)
Debug/Student.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.
