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

In this way, by knowing what communities it's in and acting on all of them at once you might be able to eradicate polio in the same way that we eradicated smallpox.

因此,通过知晓疾病的所在群体,并且一次性对整个群体做免疫尝试,也许那就可以像根除天花那样,根除小儿麻痹症

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