Implement a Basic Algorithmic Challenge

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Your question is Implement a Basic Algorithmic Challenge. Start with the requirements on the right.

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Problem

TD Mobile alerts group consecutive transactions for analysis. Given a list of merchant identifiers in transaction order and an integer k, find the length of the longest contiguous transaction window containing at most k distinct merchants.

Use a sliding-window approach that runs efficiently for large transaction streams.

Formal Specification

Implement longest_alert_window(merchants, k).

Input: merchants, a list of strings representing merchant identifiers, and k, a non-negative integer.
Output: An integer representing the maximum length of a contiguous subarray with at most k distinct merchant identifiers.
Return 0 when k is 0 or the input list is empty.

Constraints

0 <= len(merchants) <= 100,000
0 <= k <= len(merchants)
Each merchant identifier is a non-empty string
The result must use contiguous transactions

Function Signature

def longest_alert_window(merchants, k):

Your solutionPython 3

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