Insert at End of Circular Linked List in DSA C - Build from Scratch

Insert at End of Circular Linked List

📖 Scenario: You are managing a circular linked list that represents a round-robin queue of tasks. Each node holds a task number. You want to add a new task at the end of this circular list.

🎯 Goal: Build a C program that creates a circular linked list with initial tasks, sets up a new task number, inserts this new task at the end of the circular linked list, and then prints the list to show the updated order.

📋 What You'll Learn

Define a struct called Node with an integer data and a pointer next.

Create a circular linked list with exactly three nodes having data values 10, 20, and 30.

Create an integer variable called new_data and set it to 40.

Write a function called insertAtEnd that takes a pointer to the head node and an integer, and inserts a new node with that integer at the end of the circular linked list.

Print the circular linked list starting from the head node, showing all node data separated by -> and ending with (head) to indicate circularity.

💡 Why This Matters

🌍 Real World

Circular linked lists are used in real-time systems like task scheduling where the tasks repeat in a cycle.

💼 Career

Understanding circular linked lists and insertion operations is important for software engineers working on embedded systems, operating systems, and game development.

1

Create the initial circular linked list

Define a struct called Node with an integer data and a pointer next. Then create three nodes with data 10, 20, and 30 linked in a circular way. Store the pointer to the first node in a variable called head.

DSA C

// Define struct Node and create circular linked list with nodes 10, 20, 30
// Your code here

Hint

Remember to link the last node's next pointer back to head to make the list circular.

2

Add a new data variable for insertion

Create an integer variable called new_data and set it to 40.

DSA C

#include 
#include 

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

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

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

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

    third->data = 30;
    third->next = head;

    // Create new_data variable
    // Your code here

    return 0;
}

Hint

Just declare an integer variable named new_data and assign it the value 40.

3

Write the insertAtEnd function

Write a function called insertAtEnd that takes a pointer to Node called head and an integer data. This function should create a new node with data and insert it at the end of the circular linked list. The function should return the (possibly new) head pointer.

DSA C

#include 
#include 

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

Node* insertAtEnd(Node* head, int data) {
    // Write code to insert new node at end of circular linked list
    // Your code here
}

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

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

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

    third->data = 30;
    third->next = head;

    int new_data = 40;

    // Call insertAtEnd function
    // Your code here

    return 0;
}

Hint

Create a new node, find the last node by checking temp->next != head, then link the new node at the end and point it back to head.

4

Print the circular linked list

Write code to print the circular linked list starting from head. Print each node's data followed by ->. After printing all nodes, print (head) to show the list is circular.

DSA C

#include 
#include 

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

Node* insertAtEnd(Node* head, int data) {
    Node* new_node = (Node*)malloc(sizeof(Node));
    new_node->data = data;

    if (head == NULL) {
        new_node->next = new_node;
        return new_node;
    }

    Node* temp = head;
    while (temp->next != head) {
        temp = temp->next;
    }

    temp->next = new_node;
    new_node->next = head;

    return head;
}

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

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

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

    third->data = 30;
    third->next = head;

    int new_data = 40;

    head = insertAtEnd(head, new_data);

    // Print the circular linked list
    // Your code here

    return 0;
}

Hint

Use a do-while loop to print each node's data until you reach the head again, then print (head).