Dequeue Operation in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove an element from the front of the dequeue.

DSA C

int dequeueFront() {
    if (front == -1) {
        return -1; // Dequeue is empty
    }
    int data = arr[front];
    if (front == rear) {
        front = rear = -1;
    } else {
        front = [1];
    }
    return data;
}

Drag options to blanks, or click blank then click option'

Arear - 1

Bfront - 1

Crear + 1

Dfront + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Moving the front pointer backward instead of forward.

Changing the rear pointer instead of the front.

When removing from the front, we move the front pointer forward by 1.

2fill in blank

medium

Complete the code to remove an element from the rear of the dequeue.

DSA C

int dequeueRear() {
    if (rear == -1) {
        return -1; // Dequeue is empty
    }
    int data = arr[rear];
    if (front == rear) {
        front = rear = -1;
    } else {
        rear = [1];
    }
    return data;
}

Drag options to blanks, or click blank then click option'

Arear - 1

Bfront + 1

Cfront - 1

Drear + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Moving the rear pointer forward instead of backward.

Changing the front pointer instead of the rear.

When removing from the rear, we move the rear pointer backward by 1.

3fill in blank

hard

Fix the error in the condition that checks if the dequeue is empty.

DSA C

int isEmpty() {
    if ([1]) {
        return 1;
    }
    return 0;
}

Drag options to blanks, or click blank then click option'

Afront == rear

Bfront == 0 && rear == 0

Cfront == -1 && rear == -1

Dfront > rear

Attempts:

3 left

💡 Hint

Common Mistakes

Checking if front and rear are zero instead of -1.

Using front == rear which can be true when one element is present.

The dequeue is empty when both front and rear are -1.

4fill in blank

hard

Fill both blanks to correctly update the front pointer in a circular dequeue after removing from front.

DSA C

void dequeueFrontCircular() {
    if (front == -1) {
        return; // Empty dequeue
    }
    if (front == rear) {
        front = rear = -1;
    } else {
        front = (front [1] 1) [2] size;
    }
}

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A+

B-

C%

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition.

Using division instead of modulo for wrapping.

In circular dequeue, front moves forward by 1 and wraps around using modulo operator.

5fill in blank

hard

Fill all three blanks to correctly update the rear pointer in a circular dequeue after removing from rear.

DSA C

void dequeueRearCircular() {
    if (rear == -1) {
        return; // Empty dequeue
    }
    if (front == rear) {
        front = rear = -1;
    } else {
        rear = (rear [1] 1 + [2]) [3] size;
    }
}

Drag options to blanks, or click blank then click option'

A+

B-

Csize

D%

Attempts:

3 left

💡 Hint

Common Mistakes

Not adding size before modulo causing negative index.

Using addition instead of subtraction.

To move rear backward in circular dequeue, subtract 1, add size to avoid negative, then modulo size.