Fixed sliding window

Find the greatest sum of exactly k consecutive values by reusing the previous window sum.

Remember: Add entering; subtract leaving.

Example: [2,1,5,1], k=2 → maximum sum 6.

Time: O(n). Auxiliary space: O(1).

Formula: new sum = old sum + entering − leaving

Find the maximum sum of exactly k consecutive elements, including negative sums.

Complexities describe the underlying algorithm; tutorial snapshots and rendering can use additional resources.

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