Sliding Window Max Subarray Sum | Dataford Interview Questions

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Problem

Spotify analyzes contiguous windows of playlist metrics, such as track engagement scores. Given an integer array nums and a window size k, return the maximum sum among all contiguous subarrays containing exactly k elements.

Formal Specification

Implement max_subarray_sum(nums, k).

Input: nums, a non-empty list of integers, and k, an integer window size.
Output: An integer representing the largest sum of any contiguous subarray of length exactly k.
The order of elements must remain unchanged, and every candidate window must contain exactly k elements.

Use a fixed-size sliding window rather than recomputing every window from scratch.

Constraints

1 <= k <= len(nums) <= 10^5
-10^4 <= nums[i] <= 10^4
The result fits in a signed 64-bit integer

Function Signature

def max_subarray_sum(nums, k):