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I am NOT asking how to compare strings.
I am asking how to retrieve / get the actual difference between them.
Is indexing thru each character and looking for non matching ones the only way to do this ?

What I have tried:

I did try to use regular expression
Updated 16-Aug-22 9:00am
PIEBALDconsult 16-Aug-22 22:56pm    
Levenshtein Distance?

Hiow do I get the difference of (two ) strings

First, you need to define what makes the difference between 2 strings.
See those 2 strings

Either you say that all characters are different at same position.
Either you say that first char is removed and a char is added at the end.

In fact the principle of the problem is related to : diff - Wikipedia[^]. This algorithm is crafted to work with files, but it is the same principle for dtrings.
I did try to use regular expression

Probably not a good idea, RegEx are for a different usage.
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Member 14968771 15-Aug-22 15:28pm    
Lopks as I did not ( blame it on user ) explain the task. So here is visual ( I do not do u-tube (

QString one = "Hello world";
QString two =" Hello";
The difference (QString) is "world". ( How about building QStringList (split by space) and compare ( I guess I cannot get away from plain comparing ) list items ? )
Patrice T 15-Aug-22 17:01pm    
Use Improve question to update your question.
So that everyone can pay attention to this information.
There can be many scenarios:
1. The identical part of the 2 strings is shifted. For example:
2. Strings with different length
other scenarios.

To begin with, I would create a list of "use cases" and the expected outcome, and only then, go to actually program it.
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That kinda depends on what "difference between two strings" actually means.
If you have two strings "abcde" and "afbcd" is the difference a character by character comparison:
"b => f, c=> b, d => c, e => d
Or a more advance "inserted, deleted list":
"+f, -e"

What if the strings are different lengths? Does that make a difference?

Comparing strings to find actual differences can be pretty complicated, for example: Levenshtein distance - Wikipedia[^]
There is a list of different string metrics here: String metric - Wikipedia[^]

I'd say that the first thing you need to do is work out exactly what you mean by "difference", and then consider implementation after that!
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You can use strcmp (or wcscmp for UNICODE)

if ( strcmp(string1,string2) != NULL) // these strings are different
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