Arrays — DSA Interview Problems

Arrays is the contiguous, index-addressable backbone of almost every coding problem, and it shows up extremely frequently in technical interviews. Interviewers use arrays to test whether you can avoid nested-loop brute force with hashing, prefix sums, or two pointers.

Our library indexes 67 Arrays problems (30 easy, 33 medium, 4 hard), each solved brute-force → optimal in Java and Python with a line-by-line walkthrough and interview talking points. They're grouped below by the curriculum module that teaches the underlying pattern, so related problems reinforce one another.

If you remember one thing about Arrays, make it this: Most array optimisations replace a quadratic scan with a single pass plus a hash map or running aggregate. Once that clicks, the signature patterns — two pointers, sliding window, prefix sums, hashing — start to feel like a checklist you run on every new problem.