Singly Linked List – Delete Node

Q:

You are given a pointer to a node (not the tail node) in a singly linked list. Delete that node from the linked list. Write code in C.

A:

void deleteNode( Node * node )
{
Node * temp = node->next;
node->data = node->next->data;
node->next = temp->next;
free(temp);
}

DeleteList()

Q:

Write a function DeleteList() that takes a list, deallocates all of its memory and sets its
head pointer to NULL (the empty list).

A:

Delete the whole list and set the head pointer to NULL. There is a slight complication
inside the loop, since we need extract the .next pointer before we delete the node, since
after the delete it will be technically unavailable.
void DeleteList(struct node** headRef) {
struct node* current = *headRef; // deref headRef to get the real head
struct node* next;
while (current != NULL) {
next = current->next; // note the next pointer
free(current); // delete the node
current = next; // advance to the next node
}
*headRef = NULL; // Again, deref headRef to affect the real head back
// in the caller.
}

Count()

Q:

Write a Count() function that counts the number of times a given int occurs in a list.

A:
int Count(struct node* head, int searchFor) {
struct node* current = head;
int count = 0;
while (current != NULL) {
if (current->data == searchFor) count++;
current = current->next;
}
return count;
}
Alternately, the iteration may be coded with a for loop instead of a while...
int Count2(struct node* head, int searchFor) {
struct node* current;
int count = 0;
for (current = head; current != NULL; current = current->next) {
if (current->data == searchFor) count++;
}
return count;
}