Is it ok to put mat? or tiles? I was thinking of putting mat in my bedroom but my mom...

I was thinking of putting mat in my bedroom but my mom say it will cause problems when i use Air conditioner and other sort of problem. So does these of problem arise with carpet or its just my mom? gratefulness
Answers:    Lived in partially a dozen houses with nouns and carpet. Never a problem.
OMG progress with runner. Can you imagine going to the bathroom within the middle of the night and walking on cold tile within your bare foot? Brrrrr.