MATLAB: Randomly scramble letters in a single word

random

So I am trying to create a function that would take in a word when the function is called and then randomly scramble the letters within it and return that new "word" back. I am trying not to use perms, randperm or randsample as I am trying to practice while loops. A friend suggested I try this challenge out but after working on it for many hours without success, I'm trying to see if this is actually possible, and if anyone can actually get a function with an input and output to work. I don't have much to show for the code used so far as a large portion of it I accidentally deleted. I am a self taught learner.
 function output = scramble(input)
   X = size(input);
   while X > 0 
       idx = randi([1 X]);
       A(idx) = A(idx) + 1 ;
       output = X-1;
   end

Best Answer

Some suggestions:
 function output = scramble(input)
Do not use the term "input" as name of a variable, because this is an important Matlab function.
   X = size(input);
Now X is a vector. Better use numel or length.
   while X > 0
X does not change its value inside the loop. Therefore the loop will run infinitely.
       idx = randi([1 X]);
Keep code as simple as possible. Better:
       idx = randi(X);
The purpose of the next two lines is not clear to me:
       A(idx) = A(idx) + 1 ;
       output = X-1;
Together:
 function output = scramble(in)
 n   = numel(in);
 out = repmat(' ', 1, n);  % Pre-allocation
 while n > 0
    idx     = randi(n);
    out(k)  = in(idx);
    in(idx) = [];
    n       = n - 1;
 end
The iterative shrinking of the input array is a bad programming pattern and if the input is large (e.g. millions of characters), this will waste time. There are better methods for scrambling, search for "Fisher Yates Shuffle" or "Knuth Shuffle" in the net. This is the algorithm implemente in randperm when called with 2 inputs.
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