Count the number of bits that are "on" in a byte [duplicate]

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Count the number of set bits in an integer

Best algorithm to count the number of set bits in a 32-bit integer?

That's an exam question and that is all I have - "Count the number of 开发者_运维问答bits that are "on" in a byte" "On" means 1, I assume. Do I need to create a BitArray, randomly populate it and then iterate through it or is there a different way?

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Using BitArray might be efficient but you could also do

byte b = ... ;

int count = Convert.ToString(b,2).ToCharArray().Count(c => c=='1');

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Is this a interview question?

For a byte the fastest way would be to pre-compute an array such that a[i] = number of bits in i - the memory overhead is negligible.