How to split a vector into n "almost equal" parts

Question

I have a problem that I would like to merge a large number of images using ImageMagick's convert.exe, but under Windows I have a 8192 byte long command line limit.

My solution to this is to split the task into smaller sub-task, run them, and do a final task which combines them together.

My idea is to write a function, which takes a vector of images and an integer, and splits the vector into n sub-vector all having "almost equal" parts.

So for example if I would like to split 11 into 3 groups it would be 4-4-3.

Can you tell me how can I do it in C++? I mean, to write a function

split_vec( const vector<image> &images, int split )

which does the splitting?

Also, can you tell me what is the most efficient way to do if I don't need to create new vectors, just iterate through the sub-parts? Like the std::substr function with std::string?

Note: I already use Boost in the project, so if there is some nice tool in Boost for this then it's perfect for me.

Answer 1

To get a base number for the size of each part, simply divide the total by the number of parts: 11/3 = 3. Obviously some of the parts will need to be bigger than that to get the proper total, but that's just the remainder: 11 % 3 = 2. So now you know that 2 of the parts will be size 3+1, and whatever's left over will be 3.