"struct flightNode * __cdecl search(int,struct flightNode *)" (?search@@YAPAUflightNode@@HPAU1@@Z) already defined in eeeeee.obj
int __cdecl book(int,struct flightNode *)" (?book@@YAHHPAUflightNode@@@Z) already defined in eeeeee.obj
int __cdecl ask_wpassager(struct flightNode *,struct flightNode *)" (?ask_wpassager@@YAHPAUflightNode@@0@Z) already defined in eeeeee.obj
int __cdecl back_ticket(int,struct flightNode *)" (?back_ticket@@YAHHPAUflightNode@@@Z) already defined in eeeeee.obj

你是不是还有一个叫eeeeee文件？（这算什么文件名）在那里已经定义过这些函数了，而且函数签名完全一样。

没有库文件所致

问题已解决，不过还是要谢谢的！