Implement Stack Using Queue in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue size in the stack structure.

DSA C

typedef struct {
    int arr[100];
    int front, rear;
} Queue;

typedef struct {
    Queue q;
    int [1];
} Stack;

void initStack(Stack* s) {
    s->[1] = 0;
    s->q.front = 0;
    s->q.rear = -1;
}

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

Asize

Blength

Ccount

Dtop

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'size' or 'length' which are not updated properly.

Confusing queue indices with stack top.

The 'top' variable keeps track of the number of elements in the stack.

2fill in blank

medium

Complete the code to enqueue an element into the queue.

DSA C

void enqueue(Queue* q, int val) {
    q->rear++;
    q->arr[q->[1]] = val;
}

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

Arear

Bfront

Ctop

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'front' instead of 'rear' causes overwriting the wrong position.

Using 'top' which is unrelated to queue indices.

We insert the new value at the 'rear' index of the queue.

3fill in blank

hard

Fix the error in the pop function to correctly remove the top element from the stack using the queue.

DSA C

int pop(Stack* s) {
    if (s->top == 0) return -1; // empty
    int i, val;
    for (i = 0; i < s->top - 1; i++) {
        val = s->q.arr[s->q.front];
        s->q.front++;
        s->q.arr[++s->q.rear] = val;
    }
    val = s->q.arr[s->q.front];
    s->q.front++;
    s->top--;
    [1];
    return val;
}

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

As->q.front = 0

Bs->q.rear = s->q.front - 1

Cs->q.rear = s->q.front

Ds->q.front = s->q.rear

Attempts:

3 left

💡 Hint

Common Mistakes

Not updating rear causes incorrect queue state.

Setting rear equal to front causes empty queue misinterpretation.

After removing elements, rear should be reset to front - 1 to maintain queue state.

4fill in blank

hard

Fill both blanks to implement the push function that adds an element to the stack using the queue.

DSA C

void push(Stack* s, int val) {
    s->q.arr[++s->q.[1]] = val;
    s->top++;
    int i, size = s->top;
    for (i = 0; i < size - 1; i++) {
        int temp = s->q.arr[s->q.[2]];
        s->q.front++;
        s->q.arr[++s->q.rear] = temp;
    }
}

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

Arear

Bfront

Ctop

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using front instead of rear to insert new element.

Not rotating elements correctly after insertion.

We add the new element at rear and then rotate elements from front to rear to simulate stack push.

5fill in blank

hard

Fill all three blanks to implement the isEmpty function that checks if the stack is empty.

DSA C

int isEmpty(Stack* s) {
    if (s->[1] == 0 && s->q.[2] > s->q.[3]) {
        return 1;
    }
    return 0;
}

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

Atop

Bfront

Crear

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Checking only top or only queue indices.

Using size which is not maintained.

Stack is empty if top is zero and queue front is greater than rear (empty queue).