# How To Check Whether 2 Strings differ by at Least 3 Positions

Dears,

How To Check Whether 2 Strings differ by at Least 3 Positions ? Knowing that those strings have same number of characters:

To Clarify this :

Str= KTzp§64!Ae …Original String

Accepted Strings: KTzp§64sss , Kaaa§64!Ae ,KTtttt4!Ae …etc

Wherase : KTzp§64!Ae, azzp§64!Ae ,KTqq§64!Ae, KTzp§74!Ae…etc are not accepted since they are different with original one only by 2 Characters or 1;

This is C# Code for checking whether 2 strings differ by at least 3 position.
this code used 2 linq function, Zip, Sum.
zip function make new sequence with the corresponding elements of 2 sequences.
for example Two Sequence {1,2,3}, {“a”,“b”,“c”} => {(1,“a”),(2,“b”),(3,“c”)}
c# code
string1.ToCharArray().Zip(string2.ToCharArray(),(c1,c2)=>(c1==c2?0:1)).Sum();
Above c# code will sum the count of different of two strings.

Suppose both string have same length.
Loop through each string from beginning to end and increment the counter if letter matches.
If counter is 3 at the end of the loop, then that is the string you need to find.
Below code shows how to check whether letter matches at the certain index for string a and b.
`a(index).Equals(b(index)).tostring`