Insert at End Tail Insert in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Python

class Node:
    def __init__(self, data):
        self.data = [1]
        self.next = None

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

ANode

Bself

Cnext

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'self.next' instead of 'self.data' for storing data.

Assigning 'self' to data attribute.

The new node's data attribute should be set to the given data value.

2fill in blank

medium

Complete the code to check if the linked list is empty before insertion.

DSA Python

def insert_at_end(head, data):
    new_node = Node(data)
    if [1] is None:
        return new_node

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

Adata

Bnew_node

Chead

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Checking if new_node is None instead of head.

Returning None instead of new_node.

If the head is None, the list is empty, so the new node becomes the head.

3fill in blank

hard

Fix the error in the loop that finds the last node.

DSA Python

current = head
while current.[1] is not None:
    current = current.next

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

Anext

Bdata

Chead

Dprev

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'current.data' instead of 'current.next' in the loop condition.

Using 'current.prev' which does not exist in singly linked list.

To traverse the list, we follow the 'next' pointers until the last node.

4fill in blank

hard

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

DSA Python

current = head
while current.next is not None:
    current = current.next
current.[1] = [2]

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

Anext

Bdata

Cnew_node

Dhead

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning data instead of the new node.

Assigning to 'data' attribute instead of 'next'.

The last node's 'next' should point to the new node to insert it at the end.

5fill in blank

hard

Fill all three blanks to complete the insert_at_end function.

DSA Python

def insert_at_end(head, data):
    new_node = Node([1])
    if [2] is None:
        return new_node
    current = head
    while current.[3] is not None:
        current = current.next
    current.next = new_node
    return head

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

Adata

Bhead

Cnext

Dnew_node

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'new_node' instead of 'data' when creating the node.

Checking 'new_node' instead of 'head' for empty list.

Using 'data' instead of 'next' in the loop condition.

Create new node with data, check if head is None, then traverse using 'next' to insert at end.

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. Removes the last node from the list

C. Adds a new node at the beginning 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

   Other options describe removing or adding at the start, which is different.

3. Final Answer:

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

4. Quick Check:

   Insert at End = Add node at end [OK]

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

Common Mistakes:

• Confusing insert at end with insert at beginning
• Thinking it removes nodes instead of adding
• Mixing up head and tail operations

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 Python?

easy

A. new_node = Node(data); new_node.next = head; head = new_node

B. new_node = Node(data); tail = new_node; new_node.next = tail

C. new_node = Node(data); head.next = new_node; head = new_node

D. new_node = Node(data); tail.next = new_node; tail = new_node

Solution

1. Step 1: Create new node and link it after tail

   We create new_node and set tail.next to it, then update tail to new_node.

2. Step 2: Check other options for correctness

   new_node = Node(data); new_node.next = head; head = new_node inserts at head, C wrongly updates head, D sets tail before linking.

3. Final Answer:

   new_node = Node(data); tail.next = new_node; tail = new_node -> Option D

4. Quick Check:

   Tail.next = new_node, tail = new_node [OK]

Hint: Tail insert updates tail.next then tail pointer [OK]

Common Mistakes:

• Assigning new_node.next before linking to tail
• Updating head instead of tail
• Not updating tail pointer after insertion

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

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

head = Node(1)
tail = head

for value in [2, 3, 4]:
    new_node = Node(value)
    tail.next = new_node
    tail = new_node

# Print list
current = head
result = []
while current:
    result.append(current.data)
    current = current.next
print(result)

medium

A. [1, 2, 3, 4]

B. [4, 3, 2, 1]

C. [1, 2, 3]

D. [2, 3, 4]

Solution

1. Step 1: Build linked list by tail insertion

   Start with head=1, then add 2, 3, 4 at tail in order.

2. Step 2: Traverse and collect node data

   Traverse from head, collect [1, 2, 3, 4] in order.

3. Final Answer:

   [1, 2, 3, 4] -> Option A

4. Quick Check:

   Tail insert preserves order [OK]

Hint: Tail insert keeps order same as input list [OK]

Common Mistakes:

• Confusing order and reversing list
• Printing only last inserted nodes
• Not updating tail pointer correctly

4. Identify the error in this tail insert code snippet:

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

head = Node(10)
tail = head

new_node = Node(20)
new_node.next = tail
tail = new_node

medium

A. tail should be updated before assigning new_node.next

B. new_node.next should be None, not tail

C. head should be updated instead of tail

D. No error, code is correct

Solution

1. Step 1: Check linking of new_node

   new_node.next points to tail, which creates a cycle or wrong link.

2. Step 2: Correct linking for tail insert

   new_node.next should be None because it's new tail; tail.next should point to new_node.

3. Final Answer:

   new_node.next should be None, not tail -> Option B

4. Quick Check:

   New tail's next = None [OK]

Hint: New tail node's next must be None [OK]

Common Mistakes:

• Linking new_node.next to old tail
• Not updating tail.next to new_node
• Confusing head and tail pointers

5. Given a singly linked list with nodes containing values [5, 10, 15], write the sequence of steps to insert a new node with value 20 at the end, and then print the list. What will be the final printed output?

hard

A. [5, 10, 15]

B. [20, 5, 10, 15]

C. [5, 10, 15, 20]

D. [5, 10, 20, 15]

Solution

1. Step 1: Traverse to the last node (value 15)

   Start at head (5), move to 10, then 15 which is tail (next is None).

2. Step 2: Create new node with value 20 and link it

   Set last node's next to new node (20), new node's next is None.

3. Step 3: Traverse and print all nodes

   Traverse from head and collect values: 5, 10, 15, 20.

4. Final Answer:

   [5, 10, 15, 20] -> Option C

5. Quick Check:

   Tail insert adds node at end [OK]

Hint: Traverse to tail, link new node, print full list [OK]

Common Mistakes:

• Inserting new node in middle instead of end
• Not setting new node's next to None
• Forgetting to update last node's next pointer