Update q2.py

[ronakmadaann]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @ronakmadaann, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces the initial implementation for the compressed_stack_length function within q2.py. The change provides the core logic for calculating a specific "compressed stack length" based on element comparisons, moving the file from a placeholder state to having functional code.

Highlights

• q2.py function implementation: The compressed_stack_length function in q2.py has been implemented, replacing a placeholder pass statement.
• Logic for calculating compressed length: The new implementation iterates through the input list, adjusting a counter based on whether the current element is identical to the previous one. It decrements the counter for consecutive identical elements and increments it for different ones, ensuring the final returned length is non-negative.

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[gemini-code-assist]

Code Review

This pull request attempts to implement the compressed_stack_length function. However, the current implementation contains a critical logic error that leads to incorrect results for several cases. It incorrectly compares adjacent elements in the input list and mishandles the first element, instead of simulating the required stack-like cancellation behavior. I've provided a detailed comment with a corrected implementation that uses a list as a stack to accurately solve the problem.

[gemini-code-assist]

The current implementation has a critical logic flaw and does not correctly model the stack-like behavior described in the problem.

1. Incorrect Comparison: The code compares lst[i] with lst[i-1], which is the previous element in the original input list. The requirement is to compare with the "most recent active number", which is the top of the conceptual stack.
2. Edge Case i=0: When i=0, lst[i-1] accesses the last element of the list (lst[-1]), which is incorrect. The first element should always be added to the stack as there's nothing to cancel it with.

A simple counter is insufficient to solve this problem because you need to know what the last active number was. A list used as a stack is the ideal data structure for this.

Here is a corrected implementation that uses a stack to accurately track the active numbers:

    stack = []
    for num in lst:
        if stack and stack[-1] == num:
            stack.pop()
        else:
            stack.append(num)
    return len(stack)