Once each time. Right? I only do one swap potentially, it-- though not one potentially, each time at the end of the loop I do a swap.

每次循环做一次，对么？我其实,就可能做了一次交换，也许并不是可能，每次循环的结束我都得做一次交换。

麻省理工公开课 - 计算机科学及编程导论课程节选

So, a couple of weeks ago we proposed to swap two integers, and we couldn't at the time.

那么，几周前，我们提出交换两个整数，然而在那时，我们办不到。

哈佛公开课 - 计算机科学课程节选