Maximum Average Subarray I: the skills you need first

Updated Oct 7, 2026

LeetCode · easy · sliding window. Seed k cells, then slide. Max average is max sum over a fixed length.

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Skills this problem builds on

Stuck on Maximum Average Subarray I? It is usually one of these. Get each one solid and the solution stops being a trick.

1. Fix the window length in advance

   k is given. Every window has length k. You do not discover length. You slide a block of k cells.

2. Slide by dropping left and adding right

   After the first window [0,k), each step i from k to n-1 does: drop a[i-k], add a[i]. L and R both increase by 1. Length stays k.

3. Maintain the sum of the window

   Window sum updates in O(1) per move: add a[R] when R advances, subtract a[L] when L advances. After every move, sum equals a[L]+…+a[R].

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