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64+ curated questions with the same answer shape every time: quick recap, deep dive, pitfalls, and follow-ups. Coverage includes anagram palindrome problems, array basics, frequency map patterns, prefix sum, and more.
Suggested path
Topics follow a teaching order. Each answer ends with a clear Next question control so you can move forward without hunting the list.
Arrays and strings are the entry point for almost every fresher coding round — two-sum, valid anagram, longest substring without repeating characters, and their variations. This module covers the patterns interviewers recycle: two pointers (sorted arrays, palindrome checks), sliding window (subarray/substring optimisation), frequency maps (anagram detection, most frequent element), and prefix sums (range queries). Each pattern is taught with the 'why this pattern fits this shape of problem' reasoning, so you can adapt it under time pressure rather than memorising individual solutions.
Full catalog
Topics are ordered for learning. Within each topic, rows are numbered 1–64 globally so you always know where you are. Collapse topics if you want a lighter view — use Expand all when you need the full list again.
Numbers 1–64 follow the order we recommend — click any row to open the full answer, or use the sticky Next link at the bottom of each page to go Q1 → Q64.