Function sub file writing

effect : Make the code structure clearer .

step ：1, Create a suffix called .h  The header file .

2, Create a suffix called .cpp  The source file .（ Definition of amplification ）

3, Write the function declaration in the header file .

4, Write out the definition of the function in the source file .

notes ： You need to reference the header file in the defined source file .

for example ： include ”swap.h“

The header of the source file that puts the code also needs to reference the header file .