我使用自引用结构在C中创建了一个列表，我想出了如何用列表做所有可能的事情，但删除最后一个元素，这让我困惑了几个星期，请帮助我，这就是我所做的。要了解这个程序的概念，您只需要查看函数main，而且 Delete，也许 insert。请注意，tis 代码是在 linux 上使用 ubuntu 中的 gcc 编译的。
/* self-referencial structure */
struct ListNode
{
char data;
struct ListNode *nextNode ;
};
typedef struct ListNode ListNode;
typedef ListNode *ListNodePtr ;
/* function protypes */
void insert(ListNodePtr *sptr, char value); // insert element in list in alphabet order
void Delete (ListNodePtr *sptr);// PROBLEM HERE; remove last element from list
void printList(ListNodePtr);// output the contents of the list
void instructions(); // print instruction on screen
int main(void)
{
ListNodePtr startPtr = NULL ; // there are initially no nodes
int choice;
char item ;// char to be placed in list
/* Give instruction s and allow user to make a choice
* insert , print, delete.
*/
instructions();
printf("?");
scanf("%d", &choice);
/* loop until sentinel value 3 */
while (!(choice == 4) )
{
switch(choice)
{
case 1:
printf("Enter a character");
scanf("\n%c",&item);
insert(&startPtr, item);
printList(startPtr);
break ;
case 2:
/* If the list is not empty */
Delete(&startPtr);
printList(startPtr);
// if it is printf("the list is empty");
break;
case 3:
printList(startPtr);
break;
default:
printf("Invalid choice");
break;
}// end switch
printf("?");
scanf("%d",&choice);
}// end while
return 0 ;
}// END FUNCTION MAIN
/* display program choices/instruction to user */
void instructions(void)
{
printf( "Enter your choice:\n"
"1 to insert an element into the list.\n"
"2 to delete an element from the list.\n"
"3 to print the list\n"
"4 to end.\n" );
}
void insert(ListNodePtr *sptr, char value)
{
ListNodePtr currentPtr;
ListNodePtr previousPtr;
ListNodePtr newNode ;
/* create an area in memory the size of ListNode and
*allocate to newPtr */
newNode = malloc(sizeof(ListNode)); // create new node
// if space is available
if (newNode != NULL)
{
newNode->data = value;
newNode->nextNode = NULL;
previousPtr = NULL ;
currentPtr = *sptr ;
/* walk to correct location in the list */
while (currentPtr != NULL && value > currentPtr->data)
{
previousPtr = currentPtr;
currentPtr = currentPtr->nextNode;
}// end while
/* insert node at beginning of the list */
if(previousPtr == NULL)
{
newNode->nextNode = *sptr;
*sptr = newNode;
}// end if
else
{
previousPtr->nextNode = newNode;
newNode->nextNode = currentPtr ;
}
}// end if
else
{
printf("%c not inserted , memory not available", value);
}
}
void Delete(ListNodePtr *sptr)
{
ListNodePtr previousPtr;
ListNodePtr currentPtr;
ListNodePtr tempPtr;
// if there is only one element
if((*sptr)->nextNode == NULL)
{
tempPtr = *sptr; // hold on to Node being removed
*sptr = (*sptr)->nextNode;
free(tempPtr);
}
else
{
previousPtr = *sptr ;
currentPtr = (*sptr)->nextNode;
// walk to end of the list
while(currentPtr->nextNode != NULL)
{
previousPtr = *sptr;
currentPtr = currentPtr->nextNode;
}
if(currentPtr != NULL)
{
// WHAT DO I DO HERE ??!!??
// if the list has more than one two elements,
// all but the first element is deleted
previousPtr->nextNode = currentPtr->nextNode;
currentPtr = NULL ;
free(currentPtr);
}// end if
}// end else
}// END FUNCTION DELETE
void printList(ListNodePtr currentPtr)
{
if(currentPtr == NULL)
printf("List is empty");
else
{
while(currentPtr != NULL)
{
printf( "%c --> ", currentPtr->data );
currentPtr = currentPtr->nextNode;
} /* end while */
printf( "NULL\n\n" );
/* end else */
}
}