Interview Graduation
If you've worked through Chapters 1-10, stop and take stock of what you now know.
What You've Mastered
Phase 1 — The FAANG Core (Ch 1-6)
| Skill | You can now... |
|---|---|
| Mental Model | Decompose any tree problem into "this node + children" in seconds |
| Traversals | Write recursive, iterative, BFS, Morris — and choose the right one instantly |
| Bottom-Up | Solve diameter, max path sum, LCA, subtree aggregation via postorder |
| Top-Down | Solve path sums, boundary traversal, view problems via preorder |
| Construction | Build trees from traversals, serialize/deserialize, flatten |
| BSTs | Search, insert, delete, validate, kth smallest, merge |
Phase 2 — Advanced Interview (Ch 7-10)
| Skill | You can now... |
|---|---|
| Thinking Lens | See trees behind recursion, DP, backtracking, divide-and-conquer, and system design |
| Include/Exclude | Solve House Robber III, Binary Tree Cameras, vertex cover via tree DP |
| Bridge to DP | Recognize when a problem needs the DP course (rerooting, multi-state) |
| Stack Connection | Track ancestors via explicit stack, build BSTs with monotonic stack |
The Numbers
Every major tech company's tree interview questions fall within what you've learned:
| Company | Most Common Tree Questions | Your Chapter |
|---|---|---|
| Meta | Vertical Order Traversal, Binary Tree Right Side View | Ch 2, Ch 4 |
| LCA, Path Sum III, Step-by-Step Directions | Ch 3, Ch 4 | |
| Amazon | Serialize/Deserialize, BST Validate, Max Sum BST | Ch 5, Ch 6 |
| Apple | Symmetric Tree, Invert Binary Tree, Diameter | Ch 1, Ch 3 |
| Microsoft | Boundary Traversal, Kth Smallest in BST | Ch 4, Ch 6 |
Zero of these companies ask about Euler tours, binary lifting, Heavy-Light Decomposition, centroid decomposition, or Prüfer sequences in interviews.
What Comes Next
If your goal is job interviews:
You're done with trees. Go practice. Solve 30-50 LeetCode tree problems. Focus on recognizing which pattern (postorder, preorder, pair-return, include/exclude) each problem uses. Speed and pattern recognition matter more than new techniques.
Recommended practice order: 1. LC Easy trees (10 problems) — build confidence 2. LC Medium trees (20 problems) — this is interview difficulty 3. LC Hard trees (5-10 problems) — only the classics: Max Path Sum, Serialize, Binary Tree Cameras
If your goal is competitive programming:
Continue to Phase 3 (Chapters 11-16). These chapters cover: - Tree linearization (Euler tour + segment tree) - LCA with binary lifting and sparse tables - Heavy-Light Decomposition - Centroid Decomposition - DSU on tree (small-to-large merging) - Catalan numbers, Prüfer sequences, tree isomorphism
These techniques appear in Codeforces Div 1-2, ICPC regionals, and IOI. They never appear in job interviews.
If your goal is both:
Do interviews first. Get the job. Then come back for Phase 3 to sharpen your competitive edge.
The Permission to Stop
Most courses make you feel guilty for not finishing. We don't.
If you completed Chapters 1-10, you have 100% coverage of tree topics asked in software engineering interviews at every major company. The remaining chapters exist for competitive programmers, math enthusiasts, and people who find centroid decomposition genuinely fun.
There is no shame in stopping here. There is no hidden interview question lurking in Chapter 14. You are ready.
Go solve problems. Go get the job. Come back for the CP track when you're ready — it'll be here.