[Design] Big Data - Remove Duplicate Numbers - Shuatiblog.com



[Design] Big Data - Remove Duplicate Numbers - Shuatiblog.com

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2.5亿个整数中找出不重复的整数的个数,内存空间不足以容纳这2.5亿个整数。

Analysis

Categorized under 双层桶划分 or BitMap.

整数个数为232,也就是,我们可以将这232个数,划分为28个区域(比如用单个文件代表一个区域),然后将数据分离到不同的区域,然后不同的区域在利用bitmap就可以直接解决了。

But how exactly to use BitMap? 将bit-map扩展一下,用2bit表示一个数即可,0表示未出现,1表示出现一次,2表示出现2次及以上。


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