か-ないかのうちに

Usage

Used to express something happens immedeatly after. 'just as; right after; as soon as ~.'

授業が終わるか終わらないかのうちに彼は教室を出た He left the classrom as soon as class ended

彼が電車が止まるか止まらないかのうちにホームに飛び降りた He jumped onto the platform just as the train stopped