Inserting element in linked list

Question

In the linked list when we perform insertLast(int item) function, we do the following steps:

struct node *temp;
struct node *newItem;
newItem = (struct node*)malloc(sizeof(struct node));
temp = head;
while(temp->next != NULL){
 temp = temp->next;
}
temp->next = newItem;
newItem->next = NULL;

But if we do:

struct node *temp;
struct node *newItem;
newItem = (struct node*)malloc(sizeof(struct node));
temp = head;
while(temp != NULL){
 temp = temp->next;
}
temp = newItem;
newItem->next = NULL;

we get an error, why does this happen?

Answer 1

The loop

while(temp != NULL){
 ...
}

will terminate with temp == NULL, that is after running past the end of the list. Then

temp = newItem;

assigns a pointer to a newly created object to the temp variable – but that has nothing to do with a list anymore.

Hence there is no reason for any 'error' (except that the new item does not get appended to a list).

Answer 2

At the second block of code, you don't set the link from the last element to point to the newly inserted element.