Queue Implementation Using Array in DSA C - Build from Scratch

Queue Implementation Using Array

📖 Scenario: Imagine you are managing a line of customers waiting to buy tickets at a counter. You want to keep track of who is next in line using a queue. A queue works like a real line: the first person to get in line is the first person to be served.

🎯 Goal: You will build a simple queue using an array in C. You will add customers to the queue, remove them when they are served, and see the current state of the queue.

📋 What You'll Learn

Create an array to hold the queue elements

Use variables to track the front and rear positions in the queue

Implement enqueue operation to add elements to the queue

Implement dequeue operation to remove elements from the queue

Print the queue elements after operations

💡 Why This Matters

🌍 Real World

Queues are used in real life to manage lines, like customers waiting for service, print jobs waiting to print, or tasks waiting to be processed.

💼 Career

Understanding queue implementation helps in software development roles where managing ordered tasks or requests efficiently is important, such as in operating systems, web servers, and real-time systems.

1

Create the queue array and initialize front and rear

Create an integer array called queue with size 5. Create two integer variables called front and rear. Set front to -1 and rear to -1.

DSA C

# Create the queue array and initialize front and rear
// Your code here

Hint

Use int queue[5]; to create the array. Set front and rear to -1 to show the queue is empty.

2

Add two customers to the queue using enqueue logic

Add code to enqueue two customers with values 10 and 20 into the queue. Update front and rear accordingly. Use the logic: if front is -1, set it to 0. Then increase rear by 1 and add the value at queue[rear].

DSA C

int queue[5];
int front = -1;
int rear = -1;

// Enqueue 10 and 20 into the queue
// Your code here

Hint

Remember to set front to 0 only once when the first element is added. Then increase rear and add the value.

3

Remove one customer from the queue using dequeue logic

Add code to dequeue one customer from the queue. Increase front by 1 to remove the front element. If after removal front becomes greater than rear, reset both front and rear to -1 to show the queue is empty.

DSA C

int queue[5];
int front = -1;
int rear = -1;

// Enqueue 10
if (front == -1) {
    front = 0;
}
rear++;
queue[rear] = 10;

// Enqueue 20
rear++;
queue[rear] = 20;

// Dequeue one element
// Your code here

Hint

To remove the front element, increase front. If the queue becomes empty, reset both front and rear to -1.

4

Print the current queue elements

Write a for loop to print all elements in queue from front to rear. Print each element followed by a space. If the queue is empty (when front is -1), print Queue is empty.

DSA C

int queue[5];
int front = -1;
int rear = -1;

// Enqueue 10
if (front == -1) {
    front = 0;
}
rear++;
queue[rear] = 10;

// Enqueue 20
rear++;
queue[rear] = 20;

// Dequeue one element
front++;
if (front > rear) {
    front = -1;
    rear = -1;
}

// Print the queue elements
// Your code here

Hint

Use a for loop from front to rear to print elements. If empty, print Queue is empty.