change invidual characters in string

[Akillioon]

I would like to know how to access a
string = "hello you";
with
char a;
I would like for an example take out the first l and the y, then change the character value to

char a={a+2};

so the changes also will permit in the string which the characters has been taken from.

[vlad from moscow]

#include <iostream>
#include <string>
#include <cctype>

int main()
{
   std::string s = "hello you";

   std::cout << s << std::endl;

   for ( char &c : s ) c = std::toupper( c );

   std::cout << s << std::endl;

   for ( std::string::size_type i = 0; i < s.size(); i++ ) s[i] = std::tolower( s[i] );

   std::cout << s << std::endl;
}
 

[Akillioon]

Thanks for a so quick answear

[vlad from moscow]

I enlarged the example.