Stack vs Array Direct Use Why We Need Stack Abstraction in DSA Python - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an element to the stack using list append.

DSA Python

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

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

Apop

Binsert

Cappend

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop or remove instead of append.

Using insert which adds at a specific position.

We use append to add an element to the end of the list, which acts as the top of the stack.

2fill in blank

medium

Complete the code to remove the top element from the stack using list method.

DSA Python

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

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

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove which deletes by value, not position.

Using append which adds instead of removing.

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

3fill in blank

hard

Fix the error in the code that tries to use list as a stack but incorrectly accesses the top element.

DSA Python

stack = [10, 20, 30]
top = stack[1]  # get top element
print(top)

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

A[0]

B[1]

C[-2]

D[-1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 0 which is the bottom of the stack.

Using index 1 or -2 which are not the top element.

The top element of the stack is the last item in the list, accessed by index -1.

4fill in blank

hard

Fill both blanks to create a stack abstraction class with push and pop methods.

DSA Python

class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.[1](item)

    def pop(self):
        return self.items.[2]()

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

Aappend

Binsert

Cpop

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using insert instead of append for push.

Using remove instead of pop for pop method.

Use append to add items and pop to remove the top item, following stack rules.

5fill in blank

hard

Fill in the blank to implement a method that checks if the stack is empty and returns a boolean.

DSA Python

class Stack:
    def __init__(self):
        self.items = []
    def push(self, item):
        self.items.append(item)

    def is_empty(self):
        return len(self.items) [1] 0

stack = Stack()
print(stack.is_empty())  # True
stack.push(1)
print(stack.is_empty())  # False

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

A==

B>

C!=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > or < which check for non-empty incorrectly.

Using != which returns True for non-empty stacks.

Checking if length equals zero tells if the stack is empty.