No opposite sex can stay in a dorm overnight.
Any violation will result in a disciplinary action according to the Student Accommodation Policy.

housing@cc.nctu.edu.tw
No opposite sex can stay in a dorm overnight.  Any violation will result in a disciplinary action according to the Student Accommodation Policy.  He/She shall be deprived of the rights to apply for lodging and the rights to lodge.  Please report to the residence staff member or send a mail to the e-mail address “housing@cc.nctu.edu.tw” for the violation is found. 

According to the Article 5, Paragraph 9, Student Accommodation
Policy:
To safeguard dorm security, male students shall not enter a female student dorm unless approved by the Housing Service Division (Office of National Defense Education on a non-school day) but not during 5:00 p.m.~8:00 a.m. period.  Female student should not stay in male dorm during 00:00 a.m.~ 08:00 a.m. If violated, both female and male students shall be deemed as having an opposite sex to stay unlawfully and will be deprived of the right to lodge.  The dorm opening hours during relocation period will be separately announced to public.

According to the Article 5, Paragraph 10, Student Accommodation
Policy:
One who—
（1）has kept an opposite sex to stay or take shower without approval
（2） ~（6）omit
Such student shall be deprived of the right to apply for lodging and the right to lodge, and the paid and unused dorm fee shall not be refunded. Meanwhile he/she shall be subjected to penalty according to the Student Disciplinary Policy and Student Dorm Agreement.