Coding interviews have a reputation for being unpredictable, but in practice the pattern-space is narrow and well-documented. The same 15 algorithmic patterns show up at Google, at Series A startups, and everywhere in between. The candidates who fail are not failing because the problems are impossibly hard — they are failing because they ground random problems without building pattern fluency, or they aced the coding round and bombed the behavioral. This is the 2026 plan that avoids both failure modes.
What changed in 2026
- AI pair-programming is acknowledged in interviews. Many companies now conduct live-coding sessions where you can use an AI assistant but must explain every line. Pattern fluency matters more than syntax recall.
- System design is asked earlier. Companies at the L4/L5 level now include at least one system design question; don't skip it assuming you're too junior.
- Take-home projects replaced phone screens at some companies — read the job description; prepare accordingly.
- The NeetCode 150 is effectively the industry syllabus. If you can solve those 150 problems and explain your reasoning, you're ready for 95% of loops.
The 12-week plan
| Weeks |
Focus |
Hours/week |
| 1–2 |
Arrays, strings, hash maps |
5–7 |
| 3–4 |
Two pointers, sliding window, stacks |
5–7 |
| 5–6 |
Binary search, trees, heaps |
5–7 |
| 7–8 |
Graphs, BFS, DFS, dynamic programming intro |
7–10 |
| 9–10 |
DP continued, backtracking, tries |
7–10 |
| 11 |
System design fundamentals |
5–7 |
| 12 |
Mock interviews + behavioral stories |
5–7 |
The 15 patterns that cover everything
1. Two pointers 9. Monotonic stack
2. Sliding window 10. Top-K / heap
3. Binary search 11. Intervals
4. Depth-first search 12. Greedy
5. Breadth-first search 13. Dynamic programming
6. Backtracking 14. Bit manipulation
7. Divide and conquer 15. Math / number theory
8. Trie
When you see a new problem, ask: which of these patterns fits? You will almost always find it.
How to practice a problem correctly
1. Read the problem. Don't code yet.
2. Restate it in your own words out loud.
3. Clarify constraints: input size, duplicates, edge cases.
4. Talk through a brute-force approach first.
5. Find the bottleneck; apply the relevant pattern.
6. Code the optimized solution.
7. Test with examples + edge cases before submitting.
8. After: state time and space complexity.
This process — not the solution — is what interviewers evaluate. A candidate who talks through a wrong approach is more hireable than one who silently produces a correct answer they can't explain.
Behavioral prep: the STAR method
Most engineers skip this. Don't. Behavioral rounds eliminate 30–40% of candidates.
Prepare a two-minute STAR story (Situation, Task, Action, Result) for each of these:
| Scenario |
Why asked |
| Hardest technical problem you solved |
Problem-solving depth |
| Time you disagreed with a teammate |
Conflict handling |
| Project you led or drove |
Ownership |
| Time you failed or made a mistake |
Self-awareness |
| Why this company |
Motivation / culture fit |
| Where you want to be in 3 years |
Growth trajectory |
Write them out. Practice saying them out loud. Time them. 90 seconds is perfect; 3 minutes loses the interviewer.
System design: the minimum viable topics
For L4/L5 interviews, know these by heart:
- URL shortener — hashing, redirect DB, scale to billions of URLs
- Rate limiter — token bucket or sliding window, Redis, distributed state
- News feed / timeline — fan-out on write vs fan-out on read tradeoff
- Key-value store — consistent hashing, replication, CAP theorem
The question is never "build the perfect system" — it's "walk me through the tradeoffs you'd consider."
Common mistakes
Jumping straight to code. Interviewers mark down candidates who start typing before clarifying requirements. Ask first.
Solving easy problems only. If you can solve every easy in 5 minutes, you're ready to move to mediums. Easy problems don't appear in most technical screens.
Ignoring edge cases. Empty input, single element, negative numbers, overflow — always ask or handle.
Skipping Big O analysis. Every solution requires a stated time and space complexity at the end. Practice saying it every time.
Not doing mock interviews. Typing solutions alone is different from talking through them with a person watching. Use Pramp or a friend.
What to skip
- Premium LeetCode for the problem set — the free tier has all 150 NeetCode problems. Buy premium only if you want company-tagged problems.
- HackerRank / Codewars for interview prep — the problem style diverges from FAANG-style interviews.
- System design courses before you have algorithms solid — get the coding rounds first, then invest in system design.
FAQ
How many LeetCode problems do I need?
Quality over quantity. 150 deeply understood problems beat 500 half-remembered ones. NeetCode 150 is the ceiling for most candidates.
Should I learn recursion or iteration first?
Learn both, but master recursion first — most tree and graph solutions are cleanest with it. Iteration is a fallback to avoid stack overflow.
How long should I prep for a FAANG loop?
8–12 weeks of focused daily practice (45–60 min/day) is typical. Less is doable if you have a strong CS foundation.
What if I get asked a problem I've never seen?
That's the point. Identify the pattern, state your approach out loud, code the brute force, then optimize. The process is what they're watching.
Where to go next