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Arrays

The most common interview topic — and the building block of almost every other data structure.

Browse 9 tutorials → Other topics

Why learn Arrays?

  • Show up in 30%+ of coding interviews.

  • Foundation for two-pointer, sliding window, and prefix-sum patterns.

  • Easy to start, deep enough to keep you sharp for years.

What you can build with Arrays

Two-pointer and sliding-window problems Prefix-sum and difference-array tricks Matrix and 2D grid problems

Arrays tutorials

9 articles

Hand-written tutorials, ordered as a recommended learning path.

  1. 01 Arrays A complete beginner's guide to JavaScript arrays — creation, indexing, the essential mutation methods, iteration, map/filter/reduce, and a first look at spread and destructuring.
  2. 02 Arrays — Intro A beginner's introduction to arrays — contiguous memory, indexing, the Python list vs C array caveat, time complexity of read/write/insert/delete, and 1D vs 2D arrays.
  3. 03 Arrays — Operations The everyday array patterns every DSA learner should know — traversal, linear search, insertion, deletion, reversal, rotation, prefix sums, Kadane's preview, and the one-pass habit.
  4. 04 Arrays — Practice Ten classic array interview problems with examples, approach, complexity, and clean Python solutions — Two Sum, Best Time to Buy/Sell Stock, Kadane's, Rotate Array, Product Except Self, and more.
  5. 05 Buy Sell Stock Walk through LeetCode 121 Best Time to Buy and Sell Stock. We go from the quadratic brute force to a clean one-pass solution tracking the running minimum.
  6. 06 Max Subarray A clear walkthrough of LeetCode 53 Maximum Subarray. We build Kadane's algorithm from first principles and contrast it with the divide and conquer approach.
  7. 07 Product Except Self Solve LeetCode 238 Product of Array Except Self in O(n) without division using prefix and suffix passes. Clean walkthrough plus interview script.
  8. 08 Rotate Image Solve LeetCode 48 Rotate Image in place by transposing and reversing each row. Walkthrough, edge cases, complexity, and interview script.
  9. 09 Spiral Matrix Solve LeetCode 54 Spiral Matrix with the four-boundary walk pattern. Clean implementation, edge cases for rectangles, complexity, and interview tips.