Introduction - If you have any usage issues, please Google them yourself
		 
Programming doubly linked list storage structure and basic operation of the design methods, including the following features:  initialize doubly linked list H (H is a single list head pointer)  turn tail interpolation using insert ' a' , ' b' , ' c' , ' d' , ' e' character five elements doubly linked list H output  output length of the doubly linked list H H  determine whether the doubly linked list is empty  double output H of the third element in the doubly linked list H output  characters element ' d' position  insert characters element in the fourth position on the element ' f'  output doubly linked list doubly linked list H H  delete the first three elements of the doubly linked list H output   release and destroy doubly linked list H