Delete by Value in Doubly Linked List in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the list is empty before deletion.

DSA C

if (head == [1]) {
    printf("List is empty.\n");
    return;
}

Drag options to blanks, or click blank then click option'

Ahead

BNULL

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of NULL for pointer comparison.

Checking head == head which is always true.

In C, an empty list's head pointer is NULL. Checking head == NULL confirms the list is empty.

2fill in blank

medium

Complete the code to traverse the list to find the node with the given value.

DSA C

struct Node* current = head;
while (current != NULL && current->data != [1]) {
    current = current->next;
}

Drag options to blanks, or click blank then click option'

ANULL

Bhead

Cvalue

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing with head or NULL instead of the value.

Using current->next instead of current->data.

We compare current->data with the value to find the node to delete.

3fill in blank

hard

Fix the error in updating the previous node's next pointer when deleting the current node.

DSA C

if (current->prev != NULL) {
    current->prev->[1] = current->next;
}

Drag options to blanks, or click blank then click option'

Anext

Bprev

Cdata

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Updating prev pointer instead of next.

Assigning to data or head which are incorrect.

We must update the previous node's next pointer to skip the current node.

4fill in blank

hard

Fill both blanks to correctly update the next node's prev pointer and handle head update.

DSA C

if (current->next != NULL) {
    current->next->[1] = current->prev;
}
if (current == [2]) {
    head = current->next;
}

Drag options to blanks, or click blank then click option'

Aprev

Bnext

Chead

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using next instead of prev for backward link.

Not updating head when deleting the first node.

The next node's prev pointer must point to current's prev. If current is head, update head to next.

5fill in blank

hard

Fill the blanks to free the node and complete the delete function.

DSA C

free([1]);
[2] = NULL;
return;

Drag options to blanks, or click blank then click option'

Acurrent

Bhead

Cvoid

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Freeing head instead of current.

Returning a value in a void function.

We free the current node, set current to NULL to avoid a dangling pointer.