String value to Char for isalpha() (C++)

Question

How do i convert a string with one letter to a char? I need this so that i can use the isalpha() function (from the cctype header) on it.
Soo... how do i exactly do it (provide simple solutions and examples on real code so that my brain understands (if you can) )?
Here's some code simulating my problem :
https://code.sololearn.com/cFLTJST00x6V/?ref=app

Answer 1

str is a string type, even with single character.
isalpha() argument should be a single character. So pass by index like

int alpha = isalpha(str[0]);