Traversal of Circular Linked List in DSA C - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Circular Linked List Traversal

What is the output of the following C code that traverses a circular linked list with 3 nodes containing values 10, 20, and 30?

DSA C

#include <stdio.h>
#include <stdlib.h>

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

int main() {
    struct Node* head = malloc(sizeof(struct Node));
    struct Node* second = malloc(sizeof(struct Node));
    struct Node* third = malloc(sizeof(struct Node));

    head->data = 10;
    head->next = second;

    second->data = 20;
    second->next = third;

    third->data = 30;
    third->next = head; // circular link

    struct Node* temp = head;
    do {
        printf("%d -> ", temp->data);
        temp = temp->next;
    } while (temp != head);
    printf("null\n");

    free(head);
    free(second);
    free(third);
    return 0;
}

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

B 10 -> 20 -> null

C 10 -> 20 -> 30 -> null

D Runtime error due to infinite loop

💡 Hint

Look carefully at the loop condition and how the traversal stops when it reaches the head again.

The traversal uses a do-while loop that prints each node's data and stops when it reaches the head node again, so it prints all nodes exactly once.

🧠 Conceptual

intermediate

Number of Nodes Traversed in Circular Linked List

If a circular linked list has 5 nodes, how many nodes will be visited during a traversal that starts at the head and stops when it reaches the head again?

A 5 nodes

B Infinite nodes

C 6 nodes

D 4 nodes

💡 Hint

Think about how the traversal stops exactly when it reaches the head again after visiting all nodes once.

The traversal visits all 5 nodes exactly once before stopping when it reaches the head again.

🔧 Debug

advanced

Identify the Bug in Circular Linked List Traversal

What error will occur when running this code snippet that attempts to traverse a circular linked list?

DSA C

struct Node* temp = head;
while (temp != NULL) {
    printf("%d -> ", temp->data);
    temp = temp->next;
}
printf("null\n");

A Compilation error due to missing semicolon

B Segmentation fault due to accessing NULL pointer

C Prints all nodes correctly and stops

D Infinite loop because temp never becomes NULL in circular list

💡 Hint

Think about what happens to temp in a circular linked list when checking for NULL.

In a circular linked list, next pointer never becomes NULL, so the while loop condition temp != NULL never becomes false, causing an infinite loop.

❓ Predict Output

advanced

Output After Modifying Circular Linked List

What is the output after inserting a new node with value 15 between nodes with values 10 and 20 in the circular linked list and then traversing it?

DSA C

#include <stdio.h>
#include <stdlib.h>

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

int main() {
    struct Node* head = malloc(sizeof(struct Node));
    struct Node* second = malloc(sizeof(struct Node));
    struct Node* third = malloc(sizeof(struct Node));
    struct Node* newNode = malloc(sizeof(struct Node));

    head->data = 10;
    second->data = 20;
    third->data = 30;
    newNode->data = 15;

    head->next = newNode;
    newNode->next = second;
    second->next = third;
    third->next = head;

    struct Node* temp = head;
    do {
        printf("%d -> ", temp->data);
        temp = temp->next;
    } while (temp != head);
    printf("null\n");

    free(head);
    free(second);
    free(third);
    free(newNode);
    return 0;
}

A 10 -> 15 -> 30 -> 20 -> null

B 10 -> 15 -> 20 -> 30 -> null

C 10 -> 20 -> 15 -> 30 -> null

D Runtime error due to incorrect linking

💡 Hint

Check the order of next pointers after insertion.

The new node with 15 is inserted between 10 and 20, so traversal prints 10, 15, 20, 30 in order.

🧠 Conceptual

expert

Detecting Circular Linked List Using Fast and Slow Pointers

Which statement correctly describes how the fast and slow pointer method detects a circular linked list?

A If fast pointer meets slow pointer, the list is circular

B If fast pointer reaches NULL, the list is circular

C If slow pointer reaches NULL, the list is circular

D If slow pointer moves twice as fast as fast pointer, the list is circular

💡 Hint

Think about when two pointers meet in a circular structure.

In a circular linked list, fast and slow pointers eventually meet at the same node, indicating a cycle.