Section checkpoint

Essential Data Structures

8 questions drawn from the 4 chapters in this section. If most land on the first try, you are ready for the next section. If not, the explanation after each answer says which idea to revisit.

Checkpoint

8 questions · first-try answers earn the most XP

1. Your function calls itself and crashes with a maximum call depth exceeded. Which data structure is the language actually using?

2. Which task should use a queue rather than a stack?

3. Why introduce a dummy head node when deleting from a list?

4. Which problem should make you reconsider using a linked list at all?

5. Which tree problem is a poor fit for recursion?

6. Why don't tree algorithms need a visited set?

7. What structure supports a running median under repeated inserts?

8. How do you get max-heap behaviour from Python's `heapq`?

What this checkpoint covers

Stack & Queue
Valid parentheses, monotonic stack teaser.
Linked List Basics
Reverse, cycle detect with fast/slow.
Trees: BFS & DFS
Traversals + max depth + level order.
Heaps & Top-K
K largest, merge K lists intuition.

Next section: Next Level (Brief)