# C# solution with two pointer and custom function to check char is alphanumeric or not

• Below is C# solution. I created my own function to check if char is alphanumeric or not.

``````public class Solution {
private bool isAlphaNuemric (char ch)
{
if ((ch -'a' >=0 && ch - 'z' <= 0) || (ch -'A' >= 0  && ch -'Z' <=0  ) || (ch -'0' >= 0 && ch -'9' <= 0))
{
return true;
} else
{
return false;
}
}

public bool IsPalindrome(string s) {
if (s == String.Empty || s.Length < 1)
return true;

int startIndex = 0;
int endIndex = s.Length - 1;
while (startIndex < endIndex )
{
// ignore all other charcter except alphnumeric
if (!isAlphaNuemric(s[startIndex]))
{
startIndex++;
continue;
}

if (!isAlphaNuemric(s[endIndex]))
{
endIndex--;
continue;
}

if (Char.ToLower(s[startIndex]) == Char.ToLower(s[endIndex]) )
{
startIndex++;
endIndex--;
} else
{
return false;
}
}
return true;
}
}
``````

• Very nice solution! I think isAlphaNumeric() might be better satisfied as one line:

``````return ((ch -'a' >=0 && ch - 'z' <= 0) || (ch -'A' >= 0  && ch -'Z' <=0  ) || (ch -'0' >= 0 && ch -'9' <= 0));
``````

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