火車或者飛機都是不錯的選擇，看你的時間安排,火車座位寬敞，有FREE WIFI

我們這次去了4個城市， 另加Gothenburg(Second largest city of Sweden)
Copenhagen to Stockholm(Flight) 1 hour($65), Stockholm to Gothenburg(Train) 3.5 hours ($38)
Gothenburg to Oslo(Bus)  3.5 hours($28)   OSLO  to Copenhagen(Flight) 1 hour ($48)

Download App OMIO you can book both flight or train
Download App VY you can book train or bus, also you can book the train/bus from airport to downtown