Delete from Beginning of 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->next

BNULL

Chead

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Checking head->next instead of head.

Using 0 instead of NULL for pointer comparison.

We check if head is NULL to know if the list is empty.

2fill in blank

medium

Complete the code to move the head pointer to the next node after deletion.

DSA C

struct Node* temp = head;
head = head->[1];
free(temp);

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

Aprev

Bdata

Cnext

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next' to move head.

Not freeing the old head node.

After deleting the first node, head should point to the next node.

3fill in blank

hard

Fix the error in setting the previous pointer of the new head node to NULL.

DSA C

if (head != NULL) {
    head->[1] = NULL;
}

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

Aprev

Bnext

Cdata

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Setting 'next' to NULL instead of 'prev'.

Not checking if head is NULL before setting pointer.

The previous pointer of the new head should be set to NULL.

4fill in blank

hard

Fill both blanks to complete the function that deletes the first node of the doubly linked list.

DSA C

void deleteBeginning(struct Node** head_ref) {
    if (*head_ref == [1]) {
        return;
    }
    struct Node* temp = *head_ref;
    *head_ref = (*head_ref)->[2];
    if (*head_ref != NULL) {
        (*head_ref)->prev = NULL;
    }
    free(temp);
}

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

ANULL

Bhead

Cnext

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next' to move head.

Not checking if *head_ref is NULL before deletion.

We check if *head_ref is NULL to see if list is empty, then move head to next node.

5fill in blank

hard

Fill all three blanks to complete the main function that creates a list and deletes the first node.

DSA C

#include <stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
};

void deleteBeginning(struct Node** head_ref) {
    if (*head_ref == NULL) {
        return;
    }
    struct Node* temp = *head_ref;
    *head_ref = (*head_ref)->next;
    if (*head_ref != NULL) {
        (*head_ref)->prev = NULL;
    }
    free(temp);
}

int main() {
    struct Node* head = NULL;
    struct Node* second = NULL;
    struct Node* third = NULL;

    head = (struct Node*)malloc(sizeof(struct Node));
    second = (struct Node*)malloc(sizeof(struct Node));
    third = (struct Node*)malloc(sizeof(struct Node));

    head->data = 1;
    head->prev = NULL;
    head->next = second;

    second->data = 2;
    second->prev = head;
    second->next = third;

    third->data = 3;
    third->prev = second;
    third->next = NULL;

    deleteBeginning(&head);

    printf("List after deletion: ");
    struct Node* current = head;
    while (current != NULL) {
        printf("%d ", current->[1]);
        current = current->[2];
    }
    printf("\n");

    free(second);
    free(third);

    return [3];
}

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

Adata

Bnext

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Printing 'next' or 'prev' instead of 'data'.

Returning 1 instead of 0 from main.

Using wrong pointer to traverse the list.

Print node data, move to next node, and return 0 from main.