Node Structure and Pointer Design in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pointer to the next node in a linked list node structure.

DSA C

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

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

Apointer

Bprev

Clink

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' which is for doubly linked lists.

Using generic names like 'pointer' which are unclear.

The pointer to the next node in a linked list is conventionally named 'next'.

2fill in blank

medium

Complete the code to create a new node and assign its data field.

DSA C

struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
newNode->[1] = 10;

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

Adata

Bnext

Cvalue

Dinfo

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to assign to 'value' or 'info' which are not declared fields.

Assigning to 'next' which is a pointer, not data.

The data field in the node structure is named 'data', so we assign the value to newNode->data.

3fill in blank

hard

Fix the error in the code to correctly link two nodes in a singly linked list.

DSA C

struct Node* first = (struct Node*)malloc(sizeof(struct Node));
struct Node* second = (struct Node*)malloc(sizeof(struct Node));
first->data = 1;
second->data = 2;
first->[1] = second;

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

Aprev

Bnext

Clink

Dpointer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' which is for doubly linked lists.

Using undefined pointer names like 'link' or 'pointer'.

To link the first node to the second, assign the 'next' pointer of the first node to point to the second node.

4fill in blank

hard

Fill both blanks to declare a doubly linked list node structure with pointers to previous and next nodes.

DSA C

struct Node {
    int data;
    struct Node* [1];
    struct Node* [2];
};

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

Aprev

Bnext

Clink

Dpointer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'link' or 'pointer' which are not standard names.

Mixing up the order of 'prev' and 'next'.

In a doubly linked list, nodes have 'prev' pointer to the previous node and 'next' pointer to the next node.

5fill in blank

hard

Fill all three blanks to create a function that initializes a new node with given data and sets its pointers to NULL.

DSA C

struct Node* createNode(int value) {
    struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
    newNode->[1] = value;
    newNode->[2] = [3];
    return newNode;
}

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

Adata

Bnext

CNULL

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning value to 'next' or 'prev' instead of 'data'.

Not initializing pointers to NULL.

The function sets the 'data' field to the given value, the 'next' pointer to NULL, and returns the new node.

Practice

1. What does a typical node structure in a singly linked list contain?

easy

A. Two data fields and no pointers

B. Only a data field

C. A pointer to the previous node only

D. A data field and a pointer to the next node

Solution

1. Step 1: Understand node components

   A singly linked list node stores data and a pointer to the next node to link nodes sequentially.

2. Step 2: Identify correct structure

   Only A data field and a pointer to the next node mentions both data and a pointer to the next node, which is essential for singly linked lists.

3. Final Answer:

   A data field and a pointer to the next node -> Option D

4. Quick Check:

   Node = data + next pointer [OK]

Hint: Remember: singly linked list nodes have data + next pointer [OK]

Common Mistakes:

• Thinking nodes have only data without pointers
• Confusing singly linked list with doubly linked list structure
• Assuming nodes have pointers to previous nodes in singly linked lists

2. Which of the following is the correct syntax to define a node structure in C for a singly linked list?

easy

A. struct Node { int data; int next; };

B. struct Node { int data; Node *next; };

C. struct Node { int data; struct Node *next; };

D. struct Node { int data; struct Node next; };

Solution

1. Step 1: Check pointer declaration syntax

   In C, a pointer to the same struct type must be declared as 'struct Node *next;'.

2. Step 2: Validate each option

   struct Node { int data; struct Node *next; }; correctly uses 'struct Node *next;'. struct Node { int data; int next; }; wrongly uses 'int next;'. struct Node { int data; Node *next; }; misses 'struct' keyword. struct Node { int data; struct Node next; }; uses 'struct Node next;' which causes infinite size.

3. Final Answer:

   struct Node { int data; struct Node *next; }; -> Option C

4. Quick Check:

   Pointer syntax = struct Node *next [OK]

Hint: Use 'struct Node *next;' to declare pointer inside struct [OK]

Common Mistakes:

• Omitting 'struct' keyword before Node in pointer
• Declaring next as int instead of pointer
• Declaring next as struct Node (not pointer) causing infinite size

3. Consider the following code snippet for a singly linked list node creation and linking:

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

struct Node n1, n2;
n1.data = 10;
n2.data = 20;
n1.next = &n2;
n2.next = NULL;

printf("%d -> %d -> NULL", n1.data, n1.next->data);

What is the output of this code?

medium

A. 10 -> 20 -> NULL

B. 10 -> 0 -> NULL

C. 20 -> 10 -> NULL

D. Compilation error

Solution

1. Step 1: Understand node data and linking

   n1.data is 10, n2.data is 20. n1.next points to n2, n2.next is NULL.

2. Step 2: Trace printf statement

   Printing n1.data prints 10, n1.next->data accesses n2.data which is 20.

3. Final Answer:

   10 -> 20 -> NULL -> Option A

4. Quick Check:

   n1.data=10, n1.next->data=20 [OK]

Hint: Follow pointers step-by-step to find data values [OK]

Common Mistakes:

• Confusing pointer dereference syntax
• Assuming n1.next->data is zero or garbage
• Mixing up node data values

4. Identify the error in the following node structure definition and fix it:

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

medium

A. Change 'struct Node next;' to 'struct Node *next;'

B. Change 'int data;' to 'int *data;'

C. Remove 'struct' keyword before Node

D. Add a semicolon after struct definition

Solution

1. Step 1: Analyze the error in struct member

   Declaring 'struct Node next;' inside struct causes infinite size because it embeds the whole struct inside itself.

2. Step 2: Correct pointer usage

   To link nodes, use a pointer 'struct Node *next;' to refer to another node without embedding it.

3. Final Answer:

   Change 'struct Node next;' to 'struct Node *next;' -> Option A

4. Quick Check:

   Use pointer for next node to avoid infinite size [OK]

Hint: Use pointer for next node, not struct itself [OK]

Common Mistakes:

• Using struct Node instead of pointer causes infinite size
• Changing data type unnecessarily
• Ignoring pointer syntax rules

5. You want to design a node structure for a doubly linked list in C. Which of the following is the correct structure to hold an integer data and pointers to both previous and next nodes?

hard

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

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

C. struct Node { int data; struct Node prev; struct Node next; };

D. struct Node { int data; struct Node *next; };

Solution

1. Step 1: Understand doubly linked list node requirements

   A doubly linked list node must have data and two pointers: one to previous node and one to next node.

2. Step 2: Check pointer types and struct usage

   struct Node { int data; struct Node *prev; struct Node *next; }; correctly declares pointers to struct Node for prev and next. struct Node { int data; struct Node prev; struct Node next; }; wrongly embeds structs causing infinite size. struct Node { int data; int *prev; int *next; }; uses int pointers incorrectly. struct Node { int data; struct Node *next; }; misses prev pointer.

3. Final Answer:

   struct Node { int data; struct Node *prev; struct Node *next; }; -> Option B

4. Quick Check:

   Doubly linked list node = data + prev pointer + next pointer [OK]

Hint: Doubly linked list nodes have prev and next pointers [OK]

Common Mistakes:

• Embedding struct instead of using pointers
• Using wrong pointer types for prev and next
• Omitting prev pointer in doubly linked list node