Coding Practice: Arrays

TL;DR

• Arrays are still the highest-frequency interview surface for frontend engineers.
• The useful patterns are indexing, prefix accumulation, interval thinking, in-place mutation, and state transformation.
• I practice these as data-shaping problems, not just whiteboard drills.

Context

In frontend systems, arrays show up everywhere: feed ordering, table transforms, pagination, diffing UI state, drag-and-drop reorder, timeline grouping, and analytics rollups.

The Approach

Practice these 10 medium-level questions:

1. Product of Array Except Self — build left/right products without division.
2. Rotate Array by K Steps — handle large k and in-place mutation trade-offs.
3. Merge Overlapping Intervals — useful for timeline and booking-style UI ranges.
4. Insert Interval into Sorted Ranges — merge one incoming range into an existing ordered list.
5. Spiral Matrix Traversal — index-boundary practice with rectangular inputs.
6. Minimum Size Subarray Sum — combine prefix intuition with shrinking windows.
7. Move Zeroes Stably — preserve order while compacting meaningful values.
8. Find First Missing Positive — strong in-place index mapping practice.
9. Container With Most Water — pair arrays with pointer reasoning.
10. Daily Temperatures — array output with deferred answers and monotonic thinking.

Try it in the browser

Trade-offs

• Array problems often have a brute-force answer fast, but the better interview signal is whether I can see the data movement pattern.
• In-place solutions save memory, but they can reduce readability if the mutation path gets tricky.

References

• Related: Coding Practice: Strings, Sliding Window, and Two Pointers
• Related: Coding Practice: Sorting