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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push an element onto the stack.

DSA C

void push(int stack[], int *top, int value) {
    stack[++[1]] = value;
}

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

Avalue

Btop

C*top

Dstack

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'top' instead of '*top' causes incorrect pointer usage.

Assigning value before incrementing top.

The top pointer is incremented first, then the value is assigned at that position.

2fill in blank

medium

Complete the code to pop an element from the stack.

DSA C

int pop(int stack[], int *top) {
    if (*top == -1) return -1; // stack empty
    return stack[[1]--];
}

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

A*top

Bstack

Ctop

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using prefix decrement causes wrong element to be returned.

Using 'top' instead of '*top'.

Return the current top element, then decrement the top pointer.

3fill in blank

hard

Fix the error in the stack overflow check condition.

DSA C

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

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

A*top

Btop

Cstack

DmaxSize

Attempts:

3 left

💡 Hint

Common Mistakes

Using '*top' causes compilation error.

Comparing with maxSize instead of maxSize - 1.

The top index is compared to maxSize - 1 to check if stack is full.

4fill in blank

hard

Fill both blanks to check if the stack is empty and return the top element safely.

DSA C

int safePop(int stack[], int *top) {
    if (*top [1] -1) return -1;
    return stack[[2]--];
}

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A<=

B==

C*top

Dtop

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' instead of '==' causes wrong empty check.

Using 'top' instead of '*top'.

Check if top equals -1 to detect empty stack, then return element at *top and decrement.

5fill in blank

hard

Fill all three blanks to implement a function that returns the current top element without popping it.

DSA C

int peek(int stack[], int *top) {
    if (*top [1] -1) return -1;
    return stack[[2]];
    // top remains [3]
}

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

A==

B>

C*top

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '==' causes wrong empty check.

Modifying top in peek causes stack corruption.

Check if stack is empty by comparing *top to -1, then return element at *top without changing top.