How do I organize data when number of data points is unknown?

So I have a bunch of data that looks like this,

1111111111111112222222222222333333444444444555511111111222222333..etc this is just an example. I don't know how many digits there are for each number, and sometimes the sequence goes up to 234 and sometimes to 43, it's random. What I want to do is take this data and have each string of the same digit (11111) become one digit (1) and continue from 1 all the way to the end, not start over at one again. I'm sorry if this is hard to understand, but I'm not sure how to go about this. Any help is appreciated. Thanks

[Chad Gilbert]

Could you give an example of the desired output? Also, is your input a string or a numeric array?

Answer 1

[per isakson]

This code

    str = '1111111111111112222222222222333333444444444555511111111222222333';
    str([ true, not( diff( double( str ) ) == 0 ) ])

returns

    ans =
    12345123

string in and string out

[Samuel]

Thank you, perfect!

Answer 2

[Jan]

The FEX submission RunLength contains fast C-Mex code and M-code also to solve this. The 2nd output can be ignored, because you do not need the number of occurrences.

Another method:

str = '1111111111111112222222222222333333444444444555511111111222222333';
pad = [str, '*'];
result = str(pad(1:end-1) ~= pad(2:end));

[Samuel]

This also works too, thanks!