Foundations

Episode 0 The Visual Dictionary

7 min · Java

Episode 0The Visual Dictionary

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Before we solve a single interview problem, we agree on a language. Every data structure in this course has one shape and one colour: arrays, strings, counters, matrices, hash maps, hash sets, stacks, queues, linked lists and heaps. For each one you'll see what the shape means, how to declare it in Java, and what its operations cost.

What you'll learn

  • How to read pointers, windows and the four highlight colours
  • Arrays, Strings, int[26] counters and 2D matrices, and why indexing is O(1)
  • HashMap vs HashSet: key → value vs membership only
  • Stacks, queues and deques: which end you can touch
  • Linked lists and heaps (PriorityQueue), and what makes them different

Chapters

  1. 0:00Intro
  2. 0:18How to read the pictures
  3. 0:59Variable
  4. 1:20Array
  5. 1:51String
  6. 2:24Counter: int[26]
  7. 3:01Matrix
  8. 3:36HashMap
  9. 4:14HashSet
  10. 4:50Stack
  11. 5:18Queue and deque
  12. 5:48Linked list
  13. 6:22Heap (PriorityQueue)
  14. 7:00The whole dictionary