What should I do if I collide with a classmate of the opposite sex?

It doesn't matter, everyone has everyone's characteristics, even if the same dress is worn on different people, it will have different styles. Moreover, most of the clothes we wear are not personal tailors, and there is also the possibility that others will wear the same clothes as you in the same place. This not only shows that your clothes are very popular, but also shows that you have a friend of the opposite sex who has some similar tastes with you.