如果我可以成对获得因子，那么我只需要循环到该数字的平方根。

I only need to go up to the square root of the number if I can harvest the factors in pairs. To that end, I improve the algorithm and refactor the code to Listing 3.

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假设我们希望得到这样一个查找表：它返回5到20之间各个数字的平方根。

Let's say you want a lookup table that will return square roots of Numbers between 5 and 20. A simple program can be written to generate such a table like this.

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清单5中的代码首先将该因子列表收集到目标数字的平方根，将其保存在factor变量中。

The code in Listing 5 first gathers the list of factors up to the square root of the target number, saving it in the factors variable.

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