Enqueue Using Linked List in DSA C - Build from Scratch

Enqueue Using Linked List

📖 Scenario: Imagine you are managing a line of customers waiting to buy tickets. You want to add new customers to the end of the line efficiently. We will use a linked list to represent this line.

🎯 Goal: Build a simple queue using a linked list in C. You will create the linked list node, set up the queue, add new elements to the end (enqueue), and print the queue to see the order of customers.

📋 What You'll Learn

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

Create two pointers called front and rear initialized to NULL

Write a function enqueue that adds a new node with given data at the end of the queue

Print the queue elements from front to rear

💡 Why This Matters

🌍 Real World

Queues are used in many real-life situations like lines at a bank, printer job scheduling, or task management systems.

💼 Career

Understanding how to implement queues with linked lists is important for software developers working on system design, operating systems, and real-time applications.

1

Create the Node struct and initialize queue pointers

Define a struct called Node with an integer data and a pointer next. Then create two pointers called front and rear and set both to NULL.

DSA C

# Define the Node struct and initialize front and rear pointers
# Your code here

Hint

Use typedef struct Node to define the node. Initialize front and rear as NULL pointers.

2

Create the enqueue function to add nodes

Write a function called enqueue that takes an integer value. Inside, create a new Node with data set to value and next set to NULL. If rear is NULL, set both front and rear to the new node. Otherwise, set rear->next to the new node and update rear to the new node.

DSA C

#include 
#include 

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

Node* front = NULL;
Node* rear = NULL;

// Write the enqueue function below
// Your code here

Hint

Use malloc to create a new node. Check if rear is NULL to handle empty queue. Otherwise, link the new node at the end.

3

Enqueue three values into the queue

Call the enqueue function three times to add the values 10, 20, and 30 to the queue.

DSA C

#include 
#include 

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

Node* front = NULL;
Node* rear = NULL;

void enqueue(int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;
    newNode->next = NULL;
    if (rear == NULL) {
        front = newNode;
        rear = newNode;
    } else {
        rear->next = newNode;
        rear = newNode;
    }
}

// Enqueue the values 10, 20, and 30 below
// Your code here

Hint

Call enqueue three times with the exact values 10, 20, and 30.

4

Print the queue elements from front to rear

Write a while loop that starts from front and prints each node's data followed by ->. Stop when the pointer is NULL. After the loop, print NULL to show the end of the queue.

DSA C

#include 
#include 

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

Node* front = NULL;
Node* rear = NULL;

void enqueue(int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = value;
    newNode->next = NULL;
    if (rear == NULL) {
        front = newNode;
        rear = newNode;
    } else {
        rear->next = newNode;
        rear = newNode;
    }
}

int main() {
    enqueue(10);
    enqueue(20);
    enqueue(30);

    Node* temp = front;
    // Your code here
    return 0;
}

Hint

Use a while loop to move through the linked list from front to NULL. Print each data followed by ->. Finally, print NULL.