Queue vs Stack When to Use Which in DSA C - Build Both Approaches

Queue vs Stack: When to Use Which

📖 Scenario: Imagine you are managing a line at a coffee shop and a stack of plates in the kitchen. You want to understand how to use a queue and a stack to handle these situations correctly.

🎯 Goal: You will create a simple program in C that shows how to add and remove items from a queue and a stack. This will help you see when to use each data structure.

📋 What You'll Learn

Create an array-based queue with fixed size 5

Create an array-based stack with fixed size 5

Add 3 items to both queue and stack

Remove 1 item from both queue and stack

Print the current state of queue and stack after operations

💡 Why This Matters

🌍 Real World

Queues are used in places like waiting lines, task scheduling, and printer job management. Stacks are used in undo features, expression evaluation, and backtracking algorithms.

💼 Career

Understanding when to use queues or stacks helps in writing efficient programs for real-world problems like managing tasks, processing data streams, and implementing algorithms.

1

Create the Queue and Stack arrays

Create an integer array called queue with size 5 and an integer array called stack with size 5. Also create integer variables front and rear for the queue, both set to -1, and an integer variable top for the stack set to -1.

DSA C

# Create queue and stack arrays and their index variables
// Your code here

Hint

Use arrays for queue and stack. Initialize front, rear, and top to -1 to show they are empty.

2

Add 3 items to the Queue and Stack

Add the integers 10, 20, and 30 to the queue using rear to track the last item, and to the stack using top to track the last item. Update front to 0 when adding the first item to the queue.

DSA C

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

int stack[5];
int top = -1;

// Add 10, 20, 30 to queue and stack
// Your code here

Hint

For the queue, set front and rear to 0 before adding the first item. For the stack, increase top before adding each item.

3

Remove 1 item from the Queue and Stack

Remove one item from the queue by increasing front by 1. Remove one item from the stack by decreasing top by 1.

DSA C

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

int stack[5];
int top = -1;

// Add to queue
rear = 0;
front = 0;
queue[rear] = 10;
rear++;
queue[rear] = 20;
rear++;
queue[rear] = 30;

// Add to stack
stack[++top] = 10;
stack[++top] = 20;
stack[++top] = 30;

// Remove one item from queue and stack
// Your code here

Hint

For the queue, move front forward by 1 to remove the first item. For the stack, move top backward by 1 to remove the last item.

4

Print the current state of Queue and Stack

Print the current items in the queue from front to rear using a for loop with variable i. Then print the current items in the stack from top down to 0 using a for loop with variable j. Use printf to print each item separated by spaces. Print "Queue:" before the queue items and "Stack:" before the stack items.

DSA C

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

int stack[5];
int top = -1;

// Add to queue
rear = 0;
front = 0;
queue[rear] = 10;
rear++;
queue[rear] = 20;
rear++;
queue[rear] = 30;

// Add to stack
stack[++top] = 10;
stack[++top] = 20;
stack[++top] = 30;

// Remove one item from queue and stack
front++;
top--;

// Print queue and stack
// Your code here

Hint

Use for loops to print queue items from front to rear and stack items from top down to 0. Print labels before each list.