伯爵在二重presentation 1的号码 [英] Count number of 1's in binary representation

问题描述

有效的方式来计数的数量为O二进制重新presentation 1的个数（1）如果你有足够的内存一起玩。这是一个面试问题，我发现在一个网上论坛，但一直无人接听。有人可以提出建议，我不能想办法做到在O（1）的时间？

Efficient way to count number of 1s in the binary representation of a number in O(1) if you have enough memory to play with. This is an interview question I found on an online forum, but it had no answer. Can somebody suggest something, I cant think of a way to do it in O(1) time?

推荐答案

这就是汉明权重的问题，又名人口数。链接提及高效的实现。引用：

That's the Hamming weight problem, a.k.a. population count. The link mentions efficient implementations. Quoting:

通过无限的记忆，我们可以简单地创建的每个64位整数的汉明权的大型查找表

With unlimited memory, we could simply create a large lookup table of the Hamming weight of every 64 bit integer

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