And when I do this test, what I want to do, is say I'm going to pick the middle spot, and depending on the test, if I know it's in the upper half, I'm going to set my start at the mid point and the end stays the same, if it's in the front half I'm going to keep the front the same and I'm going to change the endpoint.

如果我知道目标数可能，再比中值点大的区间里，我可能就会把开始点设为中值点,而尾点不变，如果在小的那个区间里,就保持开始点不变而把尾点设为中值点，你们可以看到这儿的代码,就是这么做的,对不对？它是怎么做的？

麻省理工公开课 - 计算机科学及编程导论课程节选

it's clear that you want to add a vector that looks like that, because then you go from the start of this to the finish of that, you end up at the same point and you get this invisible 0 vector.

显然应该给它加上这样一个矢量,因为从这个矢量的起点指向那个矢量的终点,最终指向的是同一个点,你就得到这个不可见的零矢量

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