Why Circular Linked List and Real World Use Cases in DSA Go - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a circular linked list by linking the last node back to the head.

DSA Go

lastNode.next = [1]

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

AnewNode

Bnil

Chead

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Setting last node's next to nil breaks the circle.

Linking to a new node instead of the head creates a broken list.

In a circular linked list, the last node points back to the head node to form a circle.

2fill in blank

medium

Complete the code to traverse a circular linked list and print each node's value once.

DSA Go

current := head
for {
    fmt.Println(current.value)
    current = current.next
    if current == [1] {
        break
    }
}

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

Ahead

BnewNode

Ctail

Dnil

Attempts:

3 left

💡 Hint

Common Mistakes

Stopping at nil causes infinite loop in circular list.

Stopping at tail misses the circular nature.

Traversal stops when we reach the head again, completing one full circle.

3fill in blank

hard

Fix the error in the code that inserts a new node after the head in a circular linked list.

DSA Go

newNode.next = head.next
head.next = [1]

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

Ahead

BnewNode

Cnil

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Setting head.next to head creates a loop on itself.

Setting head.next to nil breaks the list.

To insert after head, head's next must point to the new node.

4fill in blank

hard

Fill both blanks to create a function that checks if a circular linked list is empty.

DSA Go

func isEmpty(head *Node) bool {
    return head == [1] || head.next == [2]
}

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

Anil

Bhead

CnewNode

Dtail

Attempts:

3 left

💡 Hint

Common Mistakes

Checking head.next == nil is wrong for circular lists.

Confusing newNode or tail with head.

The list is empty if head is nil or head's next points to head itself (single node circle).

5fill in blank

hard

Fill all three blanks to create a function that counts nodes in a circular linked list.

DSA Go

func countNodes(head *Node) int {
    if head == [1] {
        return 0
    }
    count := 1
    current := head.next
    for current != [2] {
        count++
        current = [3]
    }
    return count
}

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

Anil

Bhead

Ccurrent.next

Dhead.next

Attempts:

3 left

💡 Hint

Common Mistakes

Using head.next instead of head in loop condition causes infinite loop.

Not updating current to current.next inside loop.

If head is nil, list is empty. Loop until current reaches head again, incrementing count. Move current to current.next each step.

Practice

1. What is the main advantage of using a Circular Linked List over a regular singly linked list?

easy

A. It automatically sorts the elements

B. It uses less memory than a singly linked list

C. It prevents duplicate elements

D. It allows continuous traversal from any node without stopping

Solution

1. Step 1: Understand traversal in singly linked list

   A singly linked list ends at the last node which points to null, so traversal stops there.

2. Step 2: Understand traversal in circular linked list

   In a circular linked list, the last node points back to the first node, allowing continuous traversal from any node.

3. Final Answer:

   It allows continuous traversal from any node without stopping -> Option D

4. Quick Check:

   Continuous traversal = Advantage of circular linked list [OK]

Hint: Circular lists loop back to start, enabling endless traversal [OK]

Common Mistakes:

• Thinking circular lists save memory
• Assuming circular lists sort data automatically
• Believing circular lists prevent duplicates

2. Which of the following is the correct way to link the last node to the first node in a circular linked list in Go?

easy

A. lastNode.next = nil

B. lastNode.next = firstNode

C. lastNode = firstNode

D. firstNode.next = lastNode

Solution

1. Step 1: Identify the pointer to connect in circular linked list

   The last node's next pointer should point to the first node to form a circle.

2. Step 2: Match the correct syntax

   Assigning lastNode.next = firstNode correctly links the last node back to the first node.

3. Final Answer:

   lastNode.next = firstNode -> Option B

4. Quick Check:

   Link last to first = lastNode.next = firstNode [OK]

Hint: Last node's next must point to first node for circular link [OK]

Common Mistakes:

• Setting lastNode.next to nil breaks the circle
• Assigning lastNode = firstNode changes the node, not the link
• Linking firstNode.next to lastNode reverses the list

3. Consider this Go code snippet for a circular linked list traversal starting at head:

current := head
for i := 0; i < 5; i++ {
    fmt.Print(current.value, " -> ")
    current = current.next
}
fmt.Println("null")

If the circular linked list has nodes with values 10 -> 20 -> 30 -> (back to 10), what will be the printed output?

medium

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

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

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

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

Solution

1. Step 1: Understand the circular list nodes and traversal count

   The list nodes are 10 -> 20 -> 30 -> back to 10. The loop runs 5 times, printing 5 values.

2. Step 2: Trace each iteration's printed value

   Iteration 1: 10, 2: 20, 3: 30, 4: 10 (circle restarts), 5: 20.

3. Final Answer:

   10 -> 20 -> 30 -> 10 -> 20 -> null -> Option A

4. Quick Check:

   5 prints follow circular nodes: 10,20,30,10,20 [OK]

Hint: Loop 5 times, print node values cycling through 3 nodes [OK]

Common Mistakes:

• Stopping after 3 nodes ignoring circular nature
• Printing extra nodes beyond loop count
• Mixing node values order

4. The following Go code tries to insert a new node with value 40 after the last node in a circular linked list. What is the bug?

newNode := &Node{value: 40}
lastNode.next = newNode
newNode.next = nil

medium

A. newNode.next should point to the first node, not nil

B. lastNode should be updated to newNode before linking

C. newNode.value should be assigned after linking

D. The code should set lastNode.next to nil

Solution

1. Step 1: Understand circular linked list insertion rules

   In a circular linked list, the last node's next points to the first node to maintain the circle.

2. Step 2: Identify the bug in newNode.next assignment

   Setting newNode.next to nil breaks the circle; it should point to the first node instead.

3. Final Answer:

   newNode.next should point to the first node, not nil -> Option A

4. Quick Check:

   New node next must link to first node [OK]

Hint: New node's next must keep circle by pointing to first node [OK]

Common Mistakes:

• Setting newNode.next to nil breaks circular link
• Not updating lastNode pointer after insertion
• Assigning value after linking causes no error but is bad style

5. Which real-world scenario best fits the use of a circular linked list?

hard

A. Tracking unique visitors to a website

B. Storing user login history in chronological order

C. Implementing a music playlist that repeats songs endlessly

D. Maintaining a sorted list of student grades

Solution

1. Step 1: Understand circular linked list use cases

   Circular linked lists are ideal for scenarios requiring repeated cycling through elements without stopping.

2. Step 2: Match scenario with circular list advantage

   A music playlist that repeats songs endlessly fits perfectly because the list cycles back to the start after the last song.

3. Final Answer:

   Implementing a music playlist that repeats songs endlessly -> Option C

4. Quick Check:

   Endless cycling = music playlist use case [OK]

Hint: Think of repeating cycles like music playlists [OK]

Common Mistakes:

• Choosing sorted or unique data scenarios which need other structures
• Confusing chronological order with circular traversal
• Ignoring the need for endless repetition