Generate a random String in MatLab - matlab

Question

I am trying to generate an array of string from a long predefined array of chars as the following
if I have the following long string:
s= 'aardvaqrkaardwolfaajronabackabacusabvaftabalongeabandonabandzonedaba'
I want to create a group of random strings based on the following rules
the string should be between 4 and 12 chars should be end or start
with one of the following chars {j,q,v,f,x,g,b,d,z}

Answer 1

So here a solution which gives all strings which fullfill the following rules:
the starting and ending char has to be from the string:
start_end_char= 'jqvfxgbdz';
The length has to be between 4 and 8 chars long
The string has to be sequentially correct. Meaning the resulting
strings have to appear in the exact same way in the "long" string
So what am I doing?
First of all I find all the positions where the predefined starting and ending chars appear in the main string (careful I used s2 instead of s as string name).
Then I get a sorted list of those points (list_sorted)
Next thing is to get for each element a list of indices which acceptable ending chars (following rule 1 and 2 stated above). These are saved in helper which has to be a cell-datatype because of different length in the strings
last but not least I construct all those strings and save them in resulting_strings which also have to be a cell-datatype.
s2= 'aardvaqrkaardwolfaajronabackabacusabvaftabalongeabandonabandzonedaba';
start_end_char= 'jqvfxgbdz';
length_start = length(start_end_char);
%%finding all positions of possible starting/ending points
position_char= cell(1,length_start);
for k=1:length_start
position_char{k}=find(s2==start_end_char(k));
end
list_of_start_end_points=[];
%% getting an array with all starting/ending points in the given array
for k=1:length_start
list_of_start_end_points= horzcat(list_of_start_end_points,position_char{k});
end
sorted_list= sort(list_of_start_end_points);
%% getting possible combinations
helper = cell(1, length(sorted_list));
length_helper=[];
for k=1:length(sorted_list)
helper{k}=find(and(sorted_list-sorted_list(k)>=4,sorted_list-sorted_list(k)<=8));
length_helper = length_helper + length(helper);
end
resulting_strings = cell(1, length_helper);
l=1;
for k=1:length(sorted_list)
for m=1:length(helper{k})
resulting_strings{1,l} = s2(sorted_list(k):sorted_list(helper{k}(m)));
l=l+1;
end
end
This solution is using quite a few loops, while the first 2 loops are negatable (No of loops in the size of acceptable start/ending letters), the later two loops can be quite time consuming if the original string is much longer. So maybe someone will find a vectorized solution for the later loops.