#include <stdio.h>
#include<stdlib.h>
#include<assert.h>

typedef struct node { 
  int data; 
  struct node *next; 
} NodeT;

NodeT *makeNode();
NodeT *joinLL();
void showLL();
void freeLL();
int a;

int main(void){
   
   NodeT *head;
   printf("Enter an integer:");
   while (scanf("%d", &a)){
       joinLL(head, &a);
       printf("Enter an integer:");
   }
  showLL(head);
  if(scanf("%d", &a)!=1){
      printf("Done.\n");
    }
        

    freeLL(head);

    return 0;
    
}

//creat a new node
NodeT *makeNode(int v) { 
  NodeT *new = malloc(sizeof(NodeT)); 
  assert(new != NULL); 
  new->data = v; // initialise data
  new->next = NULL; // initialise link to next node
  return new; // return pointer to new node
}

//append a new element with data v at the end of list.
NodeT *joinLL(NodeT *head, int v){
    NodeT *insert=makeNode(v);
    insert -> next = NULL;  

    if (head==NULL){
        head = insert;  
    }
    else{
        NodeT *temp;
        temp=head;
        while (temp->next != NULL){
        temp=temp->next;
       }
        temp->next=insert;
    }
    return insert;
    }
     

    

void showLL(NodeT *head) {

    //iterate the entire linked list and print the data
   NodeT *p;

   for (p = head; p!=NULL; p = p->next) {
        int elements= p->data;
        printf("Done. List is %d-->", elements);
   }
}

void freeLL(NodeT *head) {
   NodeT *p, *temp;

   p = head;
   while (p != NULL) {
      temp = p->next;
      free(p);
      p = temp;
   }
}

我试了很多次运行这个函数，发现showLL函数不能打印。我的代码有什么问题吗？？我想是指针或者一些非常基本的东西，但是我是c语言新手。另外，我想输入一个非数字字符，然后打印完成。我可以写scanf（“%d”，&a）！=1吗？