Completed Q1, Q2 and Q3 solutions

[Disha-Kumar]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @Disha-Kumar, 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 delivers the initial implementations for three distinct algorithmic problems. It provides a solution for identifying 'stable' characters in a string, a method for calculating the effective length of a sequence after specific cancellation rules, and an algorithm to detect 'overloaded' users based on event frequency within a time window. The changes primarily involve adding the core logic to previously empty function stubs.

Highlights

• Q1: First Stable Character: The first_stable_character function in q1.py has been implemented. It identifies the first character in a string that appears at least twice and whose occurrences form a single continuous block. The solution uses a frequency map and a sliding window approach to check character stability.
• Q2: Compressed Stack Length: The compressed_stack_length function in q2.py has been implemented. This function calculates the number of elements remaining after processing a list where matching adjacent elements cancel each other out. A stack data structure is effectively used to simulate this cancellation process.
• Q3: Find Overloaded Users: The find_overloaded_users function in q3.py has been implemented. This function identifies users who have a high frequency of events within a specified time window. It groups events by user, sorts their timestamps, and then uses a sliding window technique to count events within the defined window and threshold.
• Q3 Docstring Discrepancy: It's important to note a discrepancy in q3.py: the function's docstring describes identifying users with '3+ events within any 10-second window', while the implemented solution uses default parameters of threshold=10 (meaning more than 10 events) and window=60 (meaning within a 60-second window). This suggests the code solves a slightly different problem than initially documented.

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[gemini-code-assist]

Code Review

This pull request provides solutions for three programming questions. The solution for Q2 is well-implemented. However, the solutions for Q1 and Q3 contain critical bugs. In Q1, the logic fails to check if a character appears at least twice before considering it stable. In Q3, there are several issues: the default parameters are incorrect, the window and threshold logic is flawed, and the function returns a list instead of the required set. I've provided specific comments and suggestions to address these problems.

[gemini-code-assist]

The current implementation incorrectly identifies characters that appear only once as stable. The problem description states that a character must appear at least twice to be considered stable. For example, for the input "abc", the function will return 'a', but the expected output is None. You need to add a check to ensure the character count is greater than one.

Suggested change

	if freq[current_char] == block_length:
	if freq[current_char] == block_length and block_length > 1:

[gemini-code-assist]

There are two logic errors here that cause incorrect behavior based on the problem description:

1. The window check > window on line 65 should be >= window. The problem asks for events within a 10-second window (i.e., duration < 10). Your current logic incorrectly includes events with a duration of exactly 10 seconds.
2. The event count check > threshold on line 68 is incorrect for a "3 or more" events condition. It should be >= threshold to correctly include cases with exactly threshold number of events.

Suggested change

	while times[right] - times[left] > window:
	left += 1
	if right - left + 1 > threshold:
	while times[right] - times[left] >= window:
	left += 1
	if right - left + 1 >= threshold:

[gemini-code-assist]

The default values for threshold and window do not match the problem's requirements of "3 or more events within a 10-second window". The defaults should be 3 for the event threshold and 10 for the time window.

Suggested change

	def find_overloaded_users(events, threshold=10, window=60):
	def find_overloaded_users(events, threshold=3, window=10):

[gemini-code-assist]

The problem description specifies that the function should return a set of user IDs. The current implementation returns a sorted list.

Suggested change

	return sorted(overloaded_users)
	return set(overloaded_users)