Peek Top Element of Stack in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the top element of the stack.

DSA C

int peek(Stack *s) {
    if (s->top == -1) {
        return -1; // stack empty
    }
    return s->array[1];
}

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

A[top]

B[s->top]

C[s->top - 1]

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong index like 0 or top-1.

Trying to access a variable named 'top' instead of s->top.

The top element is at index s->top in the array.

2fill in blank

medium

Complete the code to check if the stack is empty before peeking.

DSA C

int peek(Stack *s) {
    if ([1]) {
        return -1; // stack empty
    }
    return s->array[s->top];
}

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

As->top == -1

Bs->top == 0

Cs->top > 0

Ds->top < 0

Attempts:

3 left

💡 Hint

Common Mistakes

Checking if top is 0 instead of -1.

Using greater than or less than comparisons incorrectly.

The stack is empty when s->top is -1.

3fill in blank

hard

Fix the error in the peek function to correctly return the top element.

DSA C

int peek(Stack *s) {
    if (s->top == -1) {
        return -1;
    }
    return s->array[1];
}

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

A[s->top + 1]

B[0]

C[s->top - 1]

D[s->top]

Attempts:

3 left

💡 Hint

Common Mistakes

Using s->top + 1 which is out of bounds.

Using s->top - 1 which points to the wrong element.

The top element is at index s->top. Using s->top + 1 or others is incorrect.

4fill in blank

hard

Fill both blanks to complete the peek function that returns the top element safely.

DSA C

int peek(Stack *s) {
    if ([1]) {
        return -1;
    }
    return s->array[2];
}

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

As->top == -1

Bs->top == 0

C[s->top]

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Checking wrong condition for empty stack.

Accessing array at wrong index.

Check if stack is empty with s->top == -1 and return the element at s->array[s->top].

5fill in blank

hard

Fill all three blanks to implement a safe peek function that returns the top element or -1 if empty.

DSA C

int peek(Stack *s) {
    if ([1]) {
        return [2];
    }
    return s->array[3];
}

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

As->top == -1

B-1

C[s->top]

Ds->top == 0

Attempts:

3 left

💡 Hint

Common Mistakes

Returning wrong value when empty.

Accessing array at wrong index.

Check if stack is empty with s->top == -1, return -1 if empty, else return the top element at s->array[s->top].