Solving a Medium DSA Problem

Cloud Security Services groups consecutive security alerts into investigation windows. Given an array of alert type identifiers and an integer k, return the maximum length of a contiguous sequence containing at most k distinct alert types.

Use a sliding-window technique that expands the right boundary and moves the left boundary whenever the window becomes invalid.

Formal Specification

Implement longest_alert_window(alerts, k).

• Input: alerts, a list of integers representing alert types, and k, a non-negative integer.
• Output: An integer representing the maximum length of a contiguous subarray with at most k distinct values.
• Return 0 when alerts is empty or k is 0.