Stack Implementation Using Array in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an element to the top of the stack.

DSA Python

def push(stack, element):
    stack.[1](element)

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

Ainsert

Bremove

Cappend

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of append removes an element instead of adding one.

Using remove tries to delete a specific element, not add one.

The append method adds an element to the end of the list, which represents the top of the stack.

2fill in blank

medium

Complete the code to remove and return the top element from the stack.

DSA Python

def pop(stack):
    if len(stack) == 0:
        return None
    return stack.[1]()

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

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using append adds an element instead of removing one.

Using remove requires a value and does not return the removed element.

The pop method removes and returns the last element of the list, which is the top of the stack.

3fill in blank

hard

Fix the error in the code to check if the stack is empty.

DSA Python

def is_empty(stack):
    return len(stack) [1] 0

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

A!=

B==

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' checks if stack is not empty.

Using '>' or '<' does not correctly check for emptiness.

To check if the stack is empty, we compare the length to zero using ==.

4fill in blank

hard

Fill both blanks to peek at the top element without removing it.

DSA Python

def peek(stack):
    if len(stack) == 0:
        return None
    return stack[1][2]

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

A[0]

B[-2]

C()

D[-1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses tries to call the list as a function.

Using index 0 accesses the bottom, not the top.

Using stack[-1] accesses the last element, which is the top of the stack, without removing it.

5fill in blank

hard

Fill all three blanks to implement a function that returns the size of the stack and clears it.

DSA Python

def clear_and_size(stack):
    size = len(stack)
    stack[1]()
    return [2], [3]

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

Aclear

Bsize

Clen(stack)

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes only one element, not all.

Returning variables in wrong order or forgetting to save size.

The clear() method empties the list. We return the saved size and the current length (which is 0) using len(stack).