How to get the number of differences in a string comparison?

Question

I know I can get whether 2 strings are equal in content, but I need to be able to get the number of characters that differ in the result of comparing 2 string values.

For instance:

"aaaBaaaCaaaDaaaEaaa"
"aaaXaaaYaaaZaaaEaaa"

so the asnwer is 3 for this case.

Is there an easy way to do this, using regex, linq or any other way?

EDIT: Also the strings are VERY long. Say 10k+ characters.

Answer 1

I would simply loop over the character arrays, adding up a counter for each difference.

This will not account for strings with different lengths, however.

Answer 2

If both strings have the same length and do not have complicated Unicode characters like surrogates, you can loop through each character and increment a counter if the characters at that index in each string are different.

It is theoretically impossible to do it any faster. (You need to check every single character)

Answer 3

You can use LINQ:

string a = "aaaBaaaCaaaDaaaEaaa";
string b = "aaaXaaaYaaaZaaaEaaa";

int result = a.Zip(b, (x, y) => x == y).Count(z => !z)
           + Math.Abs(a.Length - b.Length);

A solution with a loop is probably more efficient though.

Answer 4

In case there are inserts and deletes: Levenstein distance

and here's the C# implementation

Answer 5

Hey, look at this: http://en.wikipedia.org/wiki/Hamming_distance

It will help you if you want to count deletions and insertions, not only replacements.