C ++ does not recognize the string type

Sometimes we encounter this situation: when we want to use the string type, even if we include the # include <string> header file, the compiler still does not recognize the string. the reason for this is the namespace problem. string is defined in the namespace STD. Because we do not customize a specific namespace, the compiler cannot determine which namespace to search for, thus leading to unrecognized errors.

Solution:

1. Use STD namespace: Using namespace STD;

2. Add the domain name ID: STD: String // before each string. It is troublesome to write STD: For each string.

3. Declare Using STD: string before using the string class;