﻿ C - Implement a queue using an array with insert, display

# C Exercises: Implement a queue using an array with insert, display

## C Queue: Exercise-1 with Solution

Write a C program to implement a queue using an array. Programs should contain functions for inserting elements into the queue, displaying queue elements, and checking whether the queue is empty or not.

Sample Solution:

C Code:

``````#include <stdio.h>
#define MAX_SIZE 100 // Define the maximum size of the queue

int queue[MAX_SIZE]; // Declare an array to store queue elements
int front = -1; // Initialize front of the queue
int back = -1; // Initialize back of the queue

// Function to insert an element into the queue
void enqueue(int item) {
if (back == MAX_SIZE - 1) { // Check if the queue is full
printf("Error: Queue is full\n"); // Print error message if queue is full
return; // Return from the function
}
if (front == -1) { // Check if the queue is empty
front = 0; // Set front to 0 if queue is empty
}
back++; // Increment back to insert the new element
queue[back] = item; // Insert the item into the queue
}

// Function to display the elements in the queue
void display() {
if (front == -1 || front > back) { // Check if the queue is empty
printf("Queue is empty\n"); // Print message if queue is empty
return; // Return from the function
}
printf("Queue elements are: "); // Print message to display queue elements
for (int i = front; i <= back; i++) { // Iterate over the queue elements
printf("%d ", queue[i]); // Print each element of the queue
}
printf("\n"); // Print newline after displaying all elements
}

// Function to check whether the queue is empty
int is_empty() {
if (front == -1 || front > back) { // Check if the queue is empty
return 1; // Return 1 if queue is empty
}
return 0; // Return 0 if queue is not empty
}

int main() {
printf("Initialize a queue!"); // Print message to indicate initializing a queue
// Insert some elements into the queue.
printf("\nCheck the queue is empty or not? %s\n", is_empty() ? "Yes" : "No"); // Print message to check if queue is empty
printf("\nInsert some elements into the queue:\n"); // Print message to indicate inserting elements into the queue
enqueue(1); // Insert element 1 into the queue
enqueue(2); // Insert element 2 into the queue
enqueue(3); // Insert element 3 into the queue
display(); // Display the elements of the queue
printf("\nInsert another element into the queue:\n"); // Print message to indicate inserting another element
enqueue(4); // Insert element 4 into the queue
display(); // Display the elements of the queue
printf("\nCheck the queue is empty or not? %s\n", is_empty() ? "Yes" : "No"); // Print message to check if queue is empty
return 0; // Return from the main function
}

```
```

Sample Output:

```Initialize a queue!
Check the queue is empty or not? Yes

Insert some elements into the queue:
Queue elements are: 1 2 3

Insert another element into the queue:
Queue elements are: 1 2 3 4
```

Flowchart:

C Programming Code Editor:

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