How to output random number each time a for loop repeats?

Hello, I'm trying to write a code that will ask for an input string from the user (like "Hello", for example), and generate random characters until it guesses the string you entered. Normally this code would take a long time to run, so I (tried) to make it so if it guesses a correct letter in the right spot (like the e in the second position of Hello) then it would stick there and continue guessing the remaining 4 letters until it gets the whole thing.

My problem is that the way I generate the random numbers is causing multiple letters to be randomly changed in unison. So for example when I enter 'hello' it outputs:

mqHdo

ieHBo

oemto

ueHru

fefkf

AeAPA

IeIuI

MeMCM

GeGOG

ZeZqZ

So the first guess seems alright but for some reason the last letter and first letter get 'matched up' and gets randomly mapped to the same letter. Also, the o was correct from the beginning, but it gets switched to a u at some point. I do not know why this is happening. Eventually the code spits out 5 digit strings of the same letter cycling through random letters.

To fix this, I tried throwing in rng('shuffle') to try to reset the random number generator between iterations of the loop but the problem still persists.

clear
clc
prompt = 'Enter the sentence you would like to be generated: ';
input = input(prompt,'s');
inputlength = length(input);
symbols = ['a':'z' 'A':'Z' ' '];
nums = randi(numel(symbols),[1 inputlength]);
random = symbols (nums);
compare = input == random;
comparenumber=double(compare);
disp(random)
truth=true([1 numel(compare)]);


while sum(comparenumber) < numel(compare)
    pause (1)
    for i = 1:inputlength
        compare = input == random;
        comparenumber=double(compare);
            if compare(i) == 0
                random=strrep(random,random(i),symbols(randi(numel(symbols))));
            end
    end
disp(random)
end

Answer 1

[Jos (10584)]

You can use an extra variable to keep track of the letters that were guessed correctly.

InputString = 'hello'
N = numel(InputString) ;
QC = false(1,N) ; % extra variable
while ~all(QC)
        RandomString = ... % I leave it up to you to return a random string of N characters
        RandomString(Q) = InputString(Q) ; % some letters are known already
        disp(RandomString)
        QC = RandomString == InputString ; % compare letter by letter
end

[Jacob Stamm]

Got it! Thank you, much appreciated. (Your code is so much cleaner btw).