Why Queue Exists and What Problems It Solves in DSA C - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enqueue an element at the rear of the queue.

DSA C

void enqueue(int queue[], int *rear, int value) {
    queue[++(*rear)] = [1];
}

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

Avalue

Brear

Cqueue

Dfront

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'rear' instead of 'value' to insert the element.

Using 'front' or 'queue' which are not the element to add.

The enqueue function adds the given value at the position after the current rear.

2fill in blank

medium

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

DSA C

int dequeue(int queue[], int *front, int rear) {
    if (*front == -1 || *front > rear) {
        return -1; // Queue is empty
    }
    return queue[[1]++];
}

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

Arear

B*rear

Cfront

D*front

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'front' without dereferencing, causing wrong index access.

Using 'rear' which points to the end, not the front.

The element at the current front is returned, then front is incremented to remove it from the queue.

3fill in blank

hard

Fix the error in the condition that checks if the queue is full.

DSA C

int isFull(int rear, int maxSize) {
    return rear == [1] - 1;
}

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AmaxSize + 1

Brear

CmaxSize

Dfront

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing rear with rear or front instead of maxSize.

Using maxSize + 1 which is out of bounds.

The queue is full when rear index reaches maxSize - 1, the last valid position.

4fill in blank

hard

Fill both blanks to correctly initialize the queue pointers.

DSA C

int front = [1];
int rear = [2];

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A-1

B0

C1

DmaxSize

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing front or rear to 0 which may cause off-by-one errors.

Using maxSize which is out of valid index range.

Both front and rear are initialized to -1 to indicate the queue is empty.

5fill in blank

hard

Fill the blanks to implement a circular queue condition to check if the queue is full.

DSA C

int isFull(int front, int rear, int maxSize) {
    return (rear + 1) % [1] == [2];
}

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

AmaxSize

Bfront

Crear

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Not using modulo operation causing index overflow.

Mixing up front and rear in the condition.

In a circular queue (wasting one space to distinguish full from empty), the queue is full when (rear + 1) % maxSize == front.