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Nov 21, 2023 · Fundamentals
LeetCode 42 – Trapping Rain Water: Problem Overview and Three O(n) Solution Techniques (Two‑Pointer, Prefix‑Max, Monotonic Stack)
This article explains LeetCode problem 42 “Trapping Rain Water”, detailing the problem statement, example, and three efficient O(n) solution approaches—two‑pointer, prefix‑max arrays, and a monotonic stack—each accompanied by complete Java implementations and analysis of their logic.
AlgorithmLeetCodeMonotonic Stack
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