LinkedList functions crash in c

Question

I implemented a linked list in c. when i test it, whenever i reach display function or insert at the end the program crashes. These are the functions:

    struct Node
    {
        char data;
        struct Node *next;
    };
    struct LinkedList
    {
        struct Node *head;
    };
       void insertAtBeginning(struct LinkedList *LL, char ele)
{
    struct Node *new = (struct Node*)malloc(sizeof(struct Node));
    new->data = ele;
    new->next = NULL;
    if(new->data == '\n')return;
    if(LL->head==NULL)LL->head = new;
    else
    {
        new->next=LL->head;
        LL->head=new;
    }
}
void insertAtTheEnd(struct LinkedList *LL, char ele)
{
    struct Node *new = (struct Node*) malloc(sizeof(struct Node));
    new->data = ele;
    new->next = NULL;
    if(LL->head==NULL){LL->head=new;return;}
    struct Node *current = LL->head;
    while(current->next != NULL) {current = current->next;}
    current->next = new;
}
void deleteNode(struct LinkedList* LL, char ele)
{
    struct Node *current = LL->head;
    struct Node *temp = LL->head;
    while(current->next->data!=ele && current!=NULL)current=current->next;
    temp=current->next; 
    current->next=current->next->next;
    free(temp);
}
void deleteFirstNode(struct LinkedList* LL)
{
    struct Node *temp;  
    if(LL->head != NULL)
    {
        temp = LL->head;
        LL->head = LL->head->next;
        free(temp);
    }
}
void displayLinkedList(struct LinkedList LL)
{
    struct Node *current = LL.head;
    printf("List: ");
    while(current != NULL)
    {
        printf("%c",current->data);
        current = current->next;
    }
        printf("\n");
}

This is the main:

    main()
{
    struct LinkedList LL;
    char c = '0';
    //Inserting at beginning
    printf("Type a string. Press Enter to end: ");
    while(c != '\n')
    {
        scanf("%c",&c);
        insertAtBeginning(&LL, c);  
    }
    printf("List: ");
    displayLinkedList(LL);
    printf("\n");
    //Inserting at end
    c='0';
    printf("Type a string. Press Enter to end: ");
    while(c != '\n')
    {
        scanf("%c",&c);
        insertAtTheEnd(&LL, c);     
    }
    printf("List: ");
    displayLinkedList(LL);
    printf("\n");
    //Remove
    printf("Enter a char to remove: ");
    scanf("%c",&c);
    deleteNode(&LL, c);
    printf("\n");
    printf("List: ");
    displayLinkedList(LL);
    printf("\n");
    deleteFirstNode(&LL);
    printf("List: ");
    displayLinkedList(LL);
}

of course This is done after inserting the necessary libraries.

Answer 1

you have to set NULL to next when you create element. if you do not do it, your while loop behaviour will be buggy

void insertAtTheEnd(struct LinkedList *LL, char ele)
{
    struct Node *new =  (struct Node*) malloc(sizeof(struct Node));
    new->next = NULL;
    new->data = ele;
    if(LL->head == NULL) LL->head = new;
    else
    {
    struct Node *current = LL->head;
    while(current->next != NULL) {current = current->next;}
    current->next = new;
    }
}

, and do same for other functions.

also you have to set NULL to your LinkedList.head . so, set NULL when you define LinkedList

struct LinkedList LL;
LL.head = NULL;

Answer 2

i asume the line if(current = LL->head) is wrong
bacause temp = current->next would crash if the result is NULL otherwise the code after the if statement doesnt makes sense

Answer 3

There are some instances where you will try to insert at the end. When you have something of the form node_new->next->prev = node , you must check to make sure that node_new->next is not NULL, because NULL does not have any type and thus does not have a prev field.

You may also consider making all of your functions return int , so that you can know if and what goes wrong.