Conceptual walkthrough of LeetCode #1: Two Sum — designed for AI Engineer / Anthropic Fellows interview prep. Covers: how to restate the problem in plain English, the brute force approach and why O(n²) breaks at scale, the optimization insight (trade space for time, store seen elements for O(1) lookup), and how to recognize the hashmap pattern in disguised problem statements. ChinesePod-inspired pedagogy — the 'aha' moment is repeated 3 times in different framings before you ever open LeetCode. After listening, the coding becomes implementation; the thinking is already done.
Pattern family: Arrays & Hashing (NeetCode 150). Builds toward: Group Anagrams, Top K Frequent, Longest Consecutive, prefix-sum-plus-hashmap problems.
