Is there a way to “grow” my array as my program continues?

问题

I am creating a prime generator in c++ using an array to store primes as I find them and then use them to check against potentials later. Is there a way to "grow" my array as my program continues?

回答1:

See std:vector. http://new.cplusplus.com/reference/stl/vector/

回答2:

I would use a std:vector something like this:

vector<int> primes;

then you would add primes to it by using:

primes.push_back(2);

and retrieve values from the vector by using:

primes[0];

Good luck!

回答3:

You could use a std::vector template, and use the reserve method based on an upper-bound for the prime counting function.

回答4:

It sounds like you need a vector to store primes in.

回答5:

I think your best bet is probably a std::list; whereas a vector needs to reallocate previously stored items when its reserved space is exceeded, this doesn't happen with a list.

回答6:

The usual cases where this sort of need arises also require an efficient lookup operation. My experience is to go for std::map which makes life much easier than vectors here.

回答7:

If there is any initially known limit to which you are going to go, you can just calculate the length of the array you need with this simple formula:

let N is that limit and LENGTH is the needed length of the array, so

LENGTH = N / log(N)

where the log(N) is a natural logarithm of N

for more information, see: Prime number distribution theorem.

来源：https://stackoverflow.com/questions/8373708/is-there-a-way-to-grow-my-array-as-my-program-continues