Push Using Linked List Node in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node with the given value.

DSA Typescript

const newNode = new Node([1]);

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

Ahead

Bnode

Cnext

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'node' or 'head' instead of the value.

Forgetting to pass any argument.

We create a new node by passing the value to the Node constructor.

2fill in blank

medium

Complete the code to link the new node to the current head of the list.

DSA Typescript

newNode.[1] = head;

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

Avalue

Bhead

Cnext

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' or 'head' instead of 'next'.

Using 'prev' which is for doubly linked lists.

The 'next' pointer of the new node should point to the current head.

3fill in blank

hard

Fix the error in updating the head pointer to the new node.

DSA Typescript

head = [1];

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

AnewNode.next

BnewNode

Chead.next

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning head to newNode.next which skips the new node.

Assigning head to null which empties the list.

The head must point to the new node after insertion.

4fill in blank

hard

Fill both blanks to complete the push function that inserts a new node at the front.

DSA Typescript

function push(value: number) {
  const newNode = new Node([1]);
  newNode.[2] = head;
  head = newNode;
}

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

Avalue

Bnext

Cprev

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next'.

Not linking the new node to the existing list.

We create a new node with the value and link its next to the current head.

5fill in blank

hard

Fill all three blanks to complete the push function with proper node creation, linking, and head update.

DSA Typescript

function push(value: number) {
  const newNode = new Node([1]);
  newNode.[2] = [3];
  head = newNode;
}

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

Avalue

Bnext

Chead

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'prev' instead of 'next'.

Not updating head correctly.

Create a new node with value, link its next to head, then update head to newNode.

Practice

1. What does the push operation do in a linked list when using nodes?

easy

A. Adds a new node at the beginning of the list

B. Removes the last node from the list

C. Searches for a node with a specific value

D. Deletes the first node of the list

Solution

1. Step 1: Understand push operation in linked list

   The push operation adds a new node to the start (head) of the linked list.

2. Step 2: Effect of push on linked list

   The new node becomes the new head, pointing to the previous first node.

3. Final Answer:

   Adds a new node at the beginning of the list -> Option A

4. Quick Check:

   Push means add at head = D [OK]

Hint: Push always adds node at the start of the list [OK]

Common Mistakes:

• Confusing push with pop (removal)
• Thinking push adds at the end
• Mixing push with search or delete

2. Which of the following is the correct TypeScript syntax to create a new node and push it to the front of a singly linked list?

easy

A. newNode = new Node(value); head = newNode.next;

B. const newNode = Node(value); head.next = newNode; head = newNode;

C. const newNode = new Node(value); newNode.next = head; head = newNode;

D. head = new Node(value); head.next = null;

Solution

1. Step 1: Create a new node with given value

   Use new Node(value) to create a node instance.

2. Step 2: Link new node to current head and update head

   Set newNode.next = head and then head = newNode to push at front.

3. Final Answer:

   const newNode = new Node(value); newNode.next = head; head = newNode; -> Option C

4. Quick Check:

   New node points to old head, head updated = A [OK]

Hint: New node next points to head, then head updated [OK]

Common Mistakes:

• Forgetting to link new node's next to old head
• Assigning head.next instead of newNode.next
• Not updating head to new node

3. What will be the linked list after executing this TypeScript code?

class Node {
  value: number;
  next: Node | null = null;
  constructor(value: number) { this.value = value; }
}

let head: Node | null = null;

function push(value: number) {
  const newNode = new Node(value);
  newNode.next = head;
  head = newNode;
}

push(10);
push(20);
push(30);

medium

A. null -> 10 -> 20 -> 30

B. 10 -> 20 -> 30 -> null

C. 20 -> 30 -> 10 -> null

D. 30 -> 20 -> 10 -> null

Solution

1. Step 1: Push 10 to empty list

   Head becomes node with value 10, next is null.

2. Step 2: Push 20 and then 30

   Each new node points to previous head, so order is 30 -> 20 -> 10 -> null.

3. Final Answer:

   30 -> 20 -> 10 -> null -> Option D

4. Quick Check:

   Last pushed is head = A [OK]

Hint: Last pushed node is always new head [OK]

Common Mistakes:

• Assuming push adds at tail
• Reading list in wrong order
• Confusing next pointers

4. Identify the error in this push function for a singly linked list:

function push(value: number) {
  const newNode = new Node(value);
  head.next = newNode;
  head = newNode;
}

medium

A. head might be null causing runtime error

B. head.next = newNode is missing

C. head is assigned before linking newNode

D. Node constructor is called incorrectly

Solution

1. Step 1: Check head usage before assignment

   The code uses head.next without checking if head is null.

2. Step 2: Consequence of head being null

   If list is empty (head null), accessing head.next causes runtime error.

3. Final Answer:

   head might be null causing runtime error -> Option A

4. Quick Check:

   Accessing head.next without null check = B [OK]

Hint: Always check if head is null before accessing head.next [OK]

Common Mistakes:

• Not checking for empty list before push
• Forgetting to set newNode.next
• Assigning head incorrectly

5. Given a linked list with nodes containing values [5, 15, 25] (5 is head), what will be the list after pushing 35 and then 45 using the push function?
Also, explain how the head changes after each push.

hard

A. 35 -> 45 -> 5 -> 15 -> 25 -> null; head moves to 35 then 45

B. 45 -> 35 -> 5 -> 15 -> 25 -> null; head moves to newest node each push

C. 5 -> 15 -> 25 -> 35 -> 45 -> null; head stays at 5

D. null; list is cleared after push

Solution

1. Step 1: Initial list and push 35

   Original head is 5. Push 35 creates new node 35 pointing to 5. Head updates to 35.

2. Step 2: Push 45 and update head

   Push 45 creates new node 45 pointing to 35. Head updates to 45. Final list: 45 -> 35 -> 5 -> 15 -> 25 -> null.

3. Final Answer:

   45 -> 35 -> 5 -> 15 -> 25 -> null; head moves to newest node each push -> Option B

4. Quick Check:

   Push adds at front, head updates = C [OK]

Hint: Head always points to last pushed node [OK]

Common Mistakes:

• Assuming push adds at tail
• Not updating head after push
• Confusing node order after pushes