Why is it useful to count the number of bits?

Question

I have seen numerous questions about counting the number of bits in an input insert type of, but why is this useful?

For those looking for bit counting algorithms, see here:

• Counting common bits in an unsigned length sequence
• The fastest way to count the number of bit transitions in an unsigned int
• How to count the number of given bits in a 32-bit integer?

Answer 1

You can consider a string of bits as set, with 1 representing membership in the set for the corresponding element. Therefore, counting bits gives you population countdialing.

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Answer 2

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Answer 3

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Answer 4

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countbits((x XOR (x-1)))-1;

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Let x =     00101100
Then x-1 =  00101011
x XOR x-1 = 00000111

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