How can you convert a string to an integer in C++?

The method of converting a string to an integer using the stoi() function is the most appropriate choice in this context. The stoi() function, which is part of the C++ standard library, is specifically designed to convert a string to an integer, making it a straightforward and safe option. It handles various scenarios, such as input strings that may not be valid representations of integers, by throwing exceptions when it encounters such cases. This feature enhances code reliability and allows developers to manage errors effectively.

In contrast, other options have limitations or challenges. The atoi() function can also convert strings to integers, but it does not provide the same level of error handling as stoi(). If the conversion is unsuccessful, atoi() simply returns zero, which can lead to confusion if not properly managed.

Direct assignment from a string to an integer type will not work, as C++ does not support the direct conversion without an explicit function. Finally, performing arithmetic operations to derive an integer from a string is not a conventional or efficient method; it would require additional logic that is unnecessary when using built-in functions designed for this purpose. Thus, the stoi() function stands out as the clear and effective choice in C++ for converting strings to integers.