Variable size bitset [duplicate]

Question

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• Define bitset size at initialization? 6 answers

I am practicing a question on array in which I have to find unique elements. Now for this my logic is to find the max element in the array and define the bitset for that. But problem is bitset needs a constant value so how to overcome this, below are some of my question on this:

a) Can I, by any chance, define the bitset with a variable size?
b) If not, then what is the best approach to use vector<bool> or vector<char>?
c) I know boost has a dynamic bitset but as I am doing this for learning I want to know of alternate approaches.

Answer 1

The std::bitset<N> template requires a fixed size in advance. The std::vector<bool> is the C++ standard's way of providing a variable-length bitvector, and it offers functionality similar to a bitset that can grow and shrink.

As for whether it's better or worse to use vector<char> or vector<bool>: the vector<bool> is a much more direct way of accomplishing this goal. I would start off by using it, then switch to vector<char> if the performance is unacceptable. In general, it's good to try to write the cleanest, most straightforward implementation first, then to optimize later on.

Hope this helps!