PROGRAMMING:Swap two strings

###Input format:
String 1
String 2
###Output format:
String 1
String 2
###Input example:
Here is a set of inputs. For example:
```in
hello
world
```
###Output example:
The corresponding output is given here. For example:
```out
world
hello
```







answer：If there is no answer, please comment
Use the default swap function to exchange two strings. Note that the header file contains CString