Why Doubly Linked List Over Singly Linked List in DSA C - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a node struct for a doubly linked list.

DSA C

typedef struct Node {
    int data;
    struct Node* next;
    struct Node* [1];
} Node;

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

Abefore

BpreviousNode

Cback

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'previousNode' or 'back' which are not standard names.

The pointer to the previous node in a doubly linked list is commonly named prev.

2fill in blank

medium

Complete the code to move forward in a doubly linked list.

DSA C

current = current->[1];

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Anext

Bprevious

Cprev

Dback

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' to move forward causes moving backward.

To move forward in a doubly linked list, use the next pointer.

3fill in blank

hard

Fix the error in the code to move backward in a doubly linked list.

DSA C

current = current->[1];

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

ApreviousNode

Bnext

Cprev

Dback

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'next' moves forward, not backward.

To move backward in a doubly linked list, use the prev pointer.

4fill in blank

hard

Fill both blanks to insert a new node after the current node in a doubly linked list.

DSA C

newNode->next = current->[1];
newNode->[2] = current;

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Anext

Bprev

Cprevious

Dbefore

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping next and prev pointers.

When inserting after current, newNode's next points to current's next, and newNode's prev points to current.

5fill in blank

hard

Fill all three blanks to update pointers when inserting a new node after current in a doubly linked list.

DSA C

if (current->next != NULL) {
    current->next->[1] = newNode;
}
newNode->[3] = current->next;
current->[2] = newNode;

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

Aprev

Bnext

Attempts:

3 left

💡 Hint

Common Mistakes

Not updating the next node's prev pointer.

When inserting, update the next node's prev to newNode, current's next to newNode, and newNode's next to current's old next.