Balanced Parentheses Problem Using Stack in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push an opening bracket onto the stack.

DSA Python

if char in '({[':
    stack.[1](char)

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

Ainsert

Bpop

Cremove

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() instead of append() to add elements.

Using remove() which deletes a specific element, not adding.

Using insert() without specifying index properly.

We use append() to add an element to the top of the stack (list).

2fill in blank

medium

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

DSA Python

if stack and stack[-1] == pairs[char]:
    stack.[1]()

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

Aappend

Bpop

Cclear

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using append() which adds instead of removing.

Using clear() which empties the whole list.

Using remove() which removes by value, not by position.

pop() removes the last element from the stack, which is needed here.

3fill in blank

hard

Fix the error in the condition to check if the character is a closing bracket.

DSA Python

if char in [1]:
    if not stack or stack[-1] != pairs[char]:
        return False

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

A"([{"

B"abc"

C"}])"

D"123"

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for opening brackets instead of closing brackets.

Using unrelated characters like letters or numbers.

Using incorrect bracket types.

We check if char is a closing bracket, so it must be in '})]'.

4fill in blank

hard

Fill both blanks to create a dictionary mapping closing to opening brackets and check stack emptiness.

DSA Python

pairs = [1]
return not [2](stack)

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

A{"}": "{", ")": "(", "]": "["}

B{"}": "(", ")": "{", "]": "["}

C{"}": "[", ")": "{", "]": "("}

D{"}": "[", ")": "(", "]": "{"}

Elen

Fbool

Gany

Hall

Attempts:

3 left

💡 Hint

Common Mistakes

Incorrect bracket mappings in the dictionary.

Using len(stack) instead of bool(stack) for emptiness check.

Using any() or all() which do not check emptiness.

The pairs dictionary maps closing to opening brackets correctly, and bool(stack) checks if stack is empty.

5fill in blank

hard

Fill all three blanks to complete the balanced parentheses function using stack.

DSA Python

def is_balanced(s):
    stack = []
    pairs = [1]
    for char in s:
        if char in [2]:
            stack.[3](char)
        elif char in pairs:
            if not stack or stack[-1] != pairs[char]:
                return False
            stack.pop()
    return not stack

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

A"({["

B"}])"

Cappend

D{"}": "{", ")": "(", "]": "["}

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing opening and closing brackets in pairs dictionary.

Using pop instead of append to add elements.

Checking wrong characters for opening brackets.

pairs dictionary maps closing to opening brackets, opening brackets are '({[', and append adds to stack.