Normal Queue Operations

Code

#include <stdio.h>
#include <stdlib.h>
#define MAX 10

typedef struct {
    int * arr[MAX];
    int front;
    int rear;
} Queue;

void main() {
    int choice, num, i;
    Queue queue;
    Queue *ptr = &queue;

    init(ptr);

    printf("Enter the number of elements: ");
    scanf("%d", &num);

    printf("Enter the elements: \n");
    for (i = 0; i < num; i++) {
        scanf("%d", &ptr->arr[i]);
    }
    (*ptr).front = 0;
    (*ptr).rear = num - 1;

    while (1) {
        printf("\n--- QUEUE OPERATIONS ---");
        printf("\n 1. Enqueue Element");
        printf("\n 2. Dequeue Element");
        printf("\n 3. Display Elements");
        printf("\n 4. Exit.");

        printf("\n\n Enter your choice: ");
        scanf("%d", &choice);

        switch (choice) {
            case 1:
                if (isFull(ptr))
                    printf(" Queue is full! \n");
                else
                    enqueue(ptr);
                break;
            case 2:
                if (isEmpty(ptr))
                    printf(" Queue is empty! \n");
                else
                    dequeue(ptr);
                break;
            case 3:
                display(ptr);
                break;
            case 4:
                exit(0);
            default:
                printf("\n Wrong choice! \n");
        }
    }
}

void init(Queue *ptr) {
    ptr->front = -1;
    ptr->rear = -1;
}

int isFull(Queue *ptr) {
    return ((*ptr).rear == MAX - 1);
}

int isEmpty(Queue *ptr) {
    return ((*ptr).front > (*ptr).rear);
}

void enqueue(Queue *ptr) {
    int ele;
    printf(" Enter the element: ");
    scanf("%d", &ele);
    (*ptr).arr[(ptr->rear)+1] = ele;
    (*ptr).rear += 1;
    display(ptr);
}

void dequeue(Queue *ptr) {
    printf("Element (%d) removed from index %d!", ptr->arr[ptr->front], ptr->front);
    (*ptr).front += 1;
    display(ptr);
}

void display(Queue *ptr) {
    int i;
    printf("\n Queue is: \n ");
    for (i = ptr->front; i <= ptr->rear; i++) {
        printf("%d, ", ptr->arr[i]);
    }
    printf("\n Front is: %d", ptr->front);
    printf("\n Back is: %d\n", ptr->rear);
}

Output

(For observation only. You can shorten this down as required.)

Enter the number of elements: 9
Enter the elements:
1
2
3
4
5
6
7
8
9

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 1
 Enter the element: 10

 Queue is:
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
 Front is: 0
 Back is: 9

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 1
 Queue is full!

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 2
 Element (1) removed from index 0!
 Queue is:
 2, 3, 4, 5, 6, 7, 8, 9, 10,
 Front is: 1
 Back is: 9

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 2
 Element (2) removed from index 1!
 Queue is:
 3, 4, 5, 6, 7, 8, 9, 10,
 Front is: 2
 Back is: 9

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 3

 Queue is:
 3, 4, 5, 6, 7, 8, 9, 10,
 Front is: 2
 Back is: 9

--- QUEUE OPERATIONS ---
 1. Enqueue Element
 2. Dequeue Element
 3. Display Elements
 4. Exit.

 Enter your choice: 4

Process returned 0 (0x0)   execution time : 16.432 s
Press any key to continue.