Queue vs Stack When to Use Which in DSA C - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push an element onto the stack.

DSA C

void push(Stack* s, int value) {
    if (s->top < MAX_SIZE - 1) {
        s->top[1];
        s->items[s->top] = value;
    }
}

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

A+=

B++

C-=

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using decrement operator which moves the top down.

Using assignment operators incorrectly.

We use the increment operator ++ to move the top index up by one before adding the new value.

2fill in blank

medium

Complete the code to dequeue an element from the queue.

DSA C

int dequeue(Queue* q) {
    if (q->front != q->rear) {
        int value = q->items[q->front];
        q->front[1];
        return value;
    }
    return -1; // Queue empty
}

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

A-=

B--

C+=

D++

Attempts:

3 left

💡 Hint

Common Mistakes

Using decrement operator which moves front backward.

Not updating the front index.

We use ++ to move the front index forward after removing the element.

3fill in blank

hard

Fix the error in the stack pop function to correctly return the top element.

DSA C

int pop(Stack* s) {
    if (s->top >= 0) {
        int value = s->items[s->top];
        s->top[1];
        return value;
    }
    return -1; // Stack empty
}

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

A--

B++

C+=

D-=

Attempts:

3 left

💡 Hint

Common Mistakes

Increasing the top index which causes wrong element removal.

Not updating the top index.

We use -- to decrease the top index after popping the element.

4fill in blank

hard

Fill in the blank to check if the queue is empty and reset indices.

DSA C

int isEmpty(Queue* q) {
    if (q->front [1] q->rear) {
        q->front = 0;
        q->rear = 0;
        return 1;
    }
    return 0;
}

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

A==

B!=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using != which checks for non-empty.

Using > or < which are incorrect for empty check.

The queue is empty when front and rear are equal, so we check with ==.

5fill in blank

hard

Fill all three blanks to create a stack and push an element.

DSA C

Stack* createStack() {
    Stack* s = (Stack*)malloc(sizeof([1]));
    s->top = [2];
    return s;
}

void push(Stack* s, int value) {
    if (s->top < MAX_SIZE - 1) {
        s->top[3];
        s->items[s->top] = value;
    }
}

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

AStack

B-1

C++

DQueue

Attempts:

3 left

💡 Hint

Common Mistakes

Allocating memory for wrong type.

Initializing top incorrectly.

Using wrong operator to update top.

We allocate memory for Stack, initialize top to -1, and use ++ to increment top when pushing.