c++ - Counting Alpha Chars in Array -

i trying count how many values in array wrongletters letters. have developed below structure this, not produce correct values. appears loop double counting, value of used begins increase exponentially when ran in full program. recommendations on better way this?

for (int = 0; < 26; i++)     {         if (wrongletters[i] != 0)             used += 1;               // used counts how many alpha chars in array     } 

i trying count how many values in array wrongletters letters.

supposed have

std::string wrongletters;  // input @ wrongletters 

you can count alpha chars this

size_t alphachars = 0; for(auto c : wrongletters) {      if(std::isalpha(c)) ++alphachars; }