Insert at End Tail Insert in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA C++

Node* newNode = new Node([1]);

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

Atail

BNULL

Chead

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using NULL instead of data when creating the node.

Using head or tail instead of data.

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

2fill in blank

medium

Complete the code to check if the list is empty.

DSA C++

if ([1] == NULL) {

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

Ahead

BnewNode

Ctail

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Checking tail instead of head.

Checking newNode or data which are unrelated.

The list is empty if the head pointer is NULL.

3fill in blank

hard

Fix the error in updating the tail pointer after insertion.

DSA C++

tail = [1];

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

ANULL

Btail->next

CnewNode

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning tail to head or NULL.

Assigning tail to tail->next which may be NULL.

After inserting at the end, tail should point to the new node.

4fill in blank

hard

Fill both blanks to link the new node at the end of the list.

DSA C++

tail->[1] = [2];

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

Anext

Bprev

CnewNode

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Using prev instead of next.

Assigning tail->next to head instead of newNode.

The current tail's next pointer should point to the new node.

5fill in blank

hard

Fill all three blanks to complete the tail insertion function.

DSA C++

void insertAtEnd(Node*& head, Node*& tail, int data) {
    Node* [1] = new Node(data);
    if (head == NULL) {
        head = [2];
        tail = [3];
    } else {
        tail->next = newNode;
        tail = newNode;
    }
}

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

AnewNode

Bhead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names for newNode.

Assigning tail instead of newNode to head.

Create newNode, set head and tail to newNode if list empty.

Practice

1. What does the "Insert at End (Tail Insert)" operation do in a singly linked list?

easy

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

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

C. Deletes the last node of the list

D. Deletes the first node of the list

Solution

1. Step 1: Understand the operation

   Insert at End means adding a new node after the last node in the list.

2. Step 2: Compare with other operations

   Adding at the beginning is different; deleting nodes removes them, not adds.

3. Final Answer:

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

4. Quick Check:

   Insert at End = Add node at list's tail [OK]

Hint: Tail insert always adds node after last element [OK]

Common Mistakes:

• Confusing tail insert with head insert
• Thinking it deletes nodes
• Assuming it inserts in the middle

2. Which of the following is the correct syntax to create a new node and insert it at the end of a singly linked list in C++?

easy

A. Node* newNode = new Node(data); tail->next = newNode; tail = newNode;

B. Node newNode = Node(data); tail->next = newNode; tail = newNode;

C. Node* newNode = Node(data); tail->next = newNode; tail = newNode;

D. Node newNode = new Node(data); tail->next = newNode; tail = newNode;

Solution

1. Step 1: Create a new node using pointer and dynamic allocation

   In C++, new nodes are created with 'new' keyword returning a pointer: Node* newNode = new Node(data);

2. Step 2: Link the new node to the current tail and update tail pointer

   Set tail->next = newNode; then update tail = newNode;

3. Final Answer:

   Node* newNode = new Node(data); tail->next = newNode; tail = newNode; -> Option A

4. Quick Check:

   Use pointer and new keyword for node creation [OK]

Hint: Use 'new' and pointers to create nodes in C++ [OK]

Common Mistakes:

• Not using pointers for new nodes
• Missing 'new' keyword causing errors
• Assigning object instead of pointer

3. What will be the output linked list after executing the following code?

struct Node {
  int data;
  Node* next;
  Node(int val) : data(val), next(nullptr) {}
};

Node* head = new Node(1);
Node* tail = head;

// Insert 2 at end
Node* newNode = new Node(2);
tail->next = newNode;
tail = newNode;

// Insert 3 at end
newNode = new Node(3);
tail->next = newNode;
tail = newNode;

// Print list
Node* temp = head;
while(temp != nullptr) {
  std::cout << temp->data << " -> ";
  temp = temp->next;
}
std::cout << "null";

medium

A. 1 -> 3 -> 2 -> null

B. 3 -> 2 -> 1 -> null

C. null

D. 1 -> 2 -> 3 -> null

Solution

1. Step 1: Trace node insertions

   Start with head = 1. Insert 2 at end: list is 1 -> 2. Insert 3 at end: list is 1 -> 2 -> 3.

2. Step 2: Trace print loop

   Prints nodes in order: 1, 2, 3, then prints 'null'.

3. Final Answer:

   1 -> 2 -> 3 -> null -> Option D

4. Quick Check:

   Tail insert appends nodes in order [OK]

Hint: Tail insert keeps order of insertion [OK]

Common Mistakes:

• Confusing order of nodes
• Not updating tail pointer
• Printing reversed list

4. Identify the error in the following code snippet for inserting a node at the end of a singly linked list:

Node* newNode = new Node(5);
tail = newNode;
tail->next = nullptr;

medium

A. The new node should be created without 'new'

B. The new node is not linked to the previous tail's next pointer

C. The new node should not have next set to nullptr

D. The tail pointer should not be updated

Solution

1. Step 1: Check linking of new node

   New node is created but previous tail's next is not updated to point to newNode.

2. Step 2: Understand tail update

   Updating tail pointer before linking breaks the chain; list loses connection to new node.

3. Final Answer:

   The new node is not linked to the previous tail's next pointer -> Option B

4. Quick Check:

   Always link previous tail's next before updating tail [OK]

Hint: Link old tail's next before moving tail pointer [OK]

Common Mistakes:

• Updating tail before linking new node
• Forgetting to set previous tail's next
• Misordering pointer assignments

5. You have a singly linked list with only a head pointer (no tail pointer). Which of the following is the most efficient way to insert a new node at the end of the list?

hard

A. Traverse the entire list to find the last node, then insert the new node after it

B. Insert the new node at the head and then swap data with the last node

C. Create a tail pointer and update it during every insertion to avoid traversal

D. Insert the new node at the beginning and reverse the list

Solution

1. Step 1: Analyze insertion without tail pointer

   Without tail pointer, inserting at end requires traversing entire list each time, which is inefficient.

2. Step 2: Consider maintaining a tail pointer

   Adding a tail pointer updated on each insertion allows direct access to last node, making insertion O(1).

3. Final Answer:

   Create a tail pointer and update it during every insertion to avoid traversal -> Option C

4. Quick Check:

   Tail pointer avoids full traversal for tail insert [OK]

Hint: Keep tail pointer to insert at end efficiently [OK]

Common Mistakes:

• Ignoring tail pointer for efficiency
• Trying to swap data instead of pointers
• Reversing list unnecessarily