divide chain code to sub chain code

I want to write a function which divide chain code with n elements into m sub chain code where the first sub chain code just contains the first two elements of chain code a with iterations , the second sub chain code contains the next two elements with iterations. For example if we have chain code a a=455454545444544444445444444445444444544444445444444444444444434444343223

I want to divide it into three sub chain code :

a1=4554545454445444444454444444454444445444444454444444444444444

a2=34444343

a2=223

i have written a function for this goals but with low time proficiency . thank you for any answer.

Answer 1

[Geoff Hayes]

majed - I'm not sure if this is more efficient than what you have, but it does produce the answer that you are looking for (assuming the the input chain is a string).

chain='455454545444544444445444444445444444544444445444444444444444434444343223';

 setOf2 = chain(1);
 startIndex = 1;
 subchains  = {};

 for k=2:length(chain)

    if ismember(chain(k),setOf2)
        continue;
    else
        if length(setOf2) == 1
            setOf2 = [setOf2 ; chain(k)];
        else
            subchains = [subchains chain(startIndex:k-1)];
            startIndex = k;
            setOf2 = chain(k);
        end
    end
 end

 subchains = [subchains chain(startIndex:end)];

subchains = [subchains chain(strtIdx:end)];

setOf2 is an array of the two distinct elements that are allowed in the subchain. We iterate over each member of the chain and check to see if it is a member of (contained within) the setOf2. If yes, then we continue to the next element. If not, then we have encountered a third unique element and so have completed the a subchain (which is added to the subchains cell array) and start a new one.

Try the above and see what happens!

[majed majed]

thank you for answering .. this code is as same as what i have written . i still wondering if i can improve it. thank you