Sliding windows, two-pointer techniques, and string manipulation.

Given an array of integers nums and an integer target , return indices of the two numbers that add up to target . Download Hint: Use a single pass hash map (O(n) time).

Several industry-standard books are often available through authorized digital libraries or educational repositories. : His book Coding Interview Questions

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Use a physical or digital whiteboard to sketch out the logic before typing any code.

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, which covers algorithms, data structures, and design questions. Full texts and summaries are often shared on academic sites like ResearchGate : Author of Coding Interviews: Questions, Analysis & Solutions , available for borrowing and streaming via Internet Archive. Free Resource Collections

Serialize and deserialize a binary tree. Design an algorithm to convert a tree to a string and back. Download Hint: Use pre-order DFS with a delimiter (e.g., # for null nodes).