LeetCode 239: Sliding Window Maximum (Monotonic Queue ACERS Guide)
Title LeetCode 239: Sliding Window Maximum (Monotonic Queue ACERS Guide) Subtitle / Summary Sliding Window Maximum is the classic combo of sliding window + monotonic queue. This article follows the ACERS template with reusable engineering patterns and multi-language implementations. Estimated reading time: 12–15 minutes Tags: sliding window, monotonic queue, array SEO keywords: Sliding Window Maximum, monotonic queue, deque, O(n) Meta description: Monotonic-queue solution for Sliding Window Maximum with engineering practice and multi-language implementations. Target Readers People practicing LeetCode / Hot100 Mid-level developers who want a reusable “sliding window + monotonic queue” template Engineers working on real-time monitoring, log analytics, or risk control Background / Motivation Rolling-window maximum appears everywhere: latency monitoring, price spikes, temperature alerts, real-time smoothing, and many more. The brute-force approach recomputes max per window in O(nk), which is unacceptable for large n. The monotonic queue reduces it to O(n), making it the most practical engineering choice. ...