How to iterate character-by-character string variable c++?

Question

C++ / C#

In general, a sentence is written to the string variable. It is necessary to loop through it character by character for comparison. How to do it, preferably without a char variable?

Answer 1

str[0] for example does not suit you?

Answer 2

string str = "Hello, world!";

for (auto c : str)
{
    do_something(c);
}