Stock Span Problem Using Stack in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize an empty stack for the stock span problem.

DSA Python

stack = [1]

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

A[]

B()

C{}

Dset()

Attempts:

3 left

💡 Hint

Common Mistakes

Using {} which creates a dictionary, not a stack.

Using () which creates a tuple, which is immutable.

Using set() which is unordered and not suitable for stack.

We use a list as a stack in Python, so initializing with [] creates an empty stack.

2fill in blank

medium

Complete the code to push the current index i onto the stack.

DSA Python

stack.[1](i)

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

Ainsert

Bpop

Cremove

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() which removes an element instead of adding.

Using remove() which removes a specific value.

Using insert() which inserts at a specific position.

To add an element to the top of the stack (list), we use append().

3fill in blank

hard

Fix the error in the while loop condition to check if stack is not empty.

DSA Python

while stack and prices[stack[-1]] <= prices[[1]]:

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

Ai

Bprices

Cstack

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Using stack instead of i, which is incorrect index.

Using prices which is the list, not an index.

Using -1 which is used to access last element of stack, not current index.

We compare the price at the top index of the stack with the current price at index i.

4fill in blank

hard

Fill both blanks to calculate the span for the current day.

DSA Python

span[i] = i - [1] if stack else [2]

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

Astack[-1]

B0

C-1

Dlen(stack)

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of -1 for empty stack case.

Using len(stack) which is unrelated to index.

Using stack instead of stack[-1].

If stack is not empty, span is difference between current index and top of stack index; else span is i - (-1) which is i + 1.

5fill in blank

hard

Fill all three blanks to complete the stock span function.

DSA Python

def calculate_span(prices):
    n = len(prices)
    span = [0] * n
    stack = []
    for [1] in range(n):
        while stack and prices[stack[-1]] <= prices[[2]]:
            stack.pop()
        span[[3]] = [2] - stack[-1] if stack else [2] + 1
        stack.append([2])
    return span

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

Ai

Bj

Ck

Dm

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing index errors.

Using j or k inconsistently.

The loop variable and all index references should be consistent as i for correct indexing.