Stack Concept and LIFO Principle 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

stack = []
stack.[1](5)
print(stack)

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

Aappend

Bpop

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using remove or insert changes the wrong part of the list.

Use append to add an element to the top of the stack (end of the list).

2fill in blank

medium

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

DSA Python

stack = [1, 2, 3]
top = stack.[1]()
print(top, stack)

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

Apop

Binsert

Cappend

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using append adds an element instead of removing.

Using remove deletes a specific value, not the last element.

Use pop to remove and return the last element, 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

stack = []
if len(stack) [1] 0:
    print('Stack is empty')
else:
    print('Stack has elements')

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

A>

B==

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' checks for non-empty instead of empty.

Using '>' or '<' may give wrong results for empty stack.

Check if length equals zero to confirm the stack is empty.

4fill in blank

hard

Fill both blanks to create a stack and add two elements.

DSA Python

stack = [1]
stack.[2](10)
stack.append(20)
print(stack)

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

A[]

B{}

Clist()

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using {} creates a dictionary, not a list.

Using set() creates an unordered collection, not suitable for stack.

Use [] to create an empty list as a stack and append to add elements.

5fill in blank

hard

Fill all three blanks to pop the top element and print the stack.

DSA Python

stack = [5, 10, 15]
top = stack.[1]()
print('Popped:', top)
print('Stack now:', stack[2]stack[3])

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

Apop

B+

C[::-1]

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' instead of '+' causes an error.

Using other methods than pop to remove the top element.

Use pop() to remove the top element. The print shows the stack plus its reversed version using + [::-1].