For a coding interview refresher after a break, review in this order: your interview language and its standard library, Big-O analysis, then the dozen or so core problem patterns, re-solving problems you have seen before rather than starting with new hard ones. After that, move to timed, mixed practice and finish with mock rounds where you explain your thinking out loud. Three weeks of one to two hours a day is enough for most experienced engineers to feel ready for a standard coding round.
Being away from interview-style problems is normal. Most day-to-day engineering looks nothing like a 45-minute algorithm round, so the rust you feel is about format, not ability. If you were recently laid off, the guide to what to do after a tech layoff covers the steps around this one.
What should I review first for a coding interview after a break?
- Your language, cold. Pick one language and make the basics automatic again: hash maps, sets, arrays and strings, sorting with a custom key, a heap or priority queue, a double-ended queue, and how to write a quick class. Forgotten syntax can cost you more time in a round than the algorithm itself.
- Big-O. Be able to state the time and space complexity of anything you write, and to say why one approach beats another. Refresh this in an afternoon with the Big-O cheat sheet and the Big-O complexity visualizer.
- Core patterns. Many interview problems are variations of a small set of patterns. Recognizing the pattern is the skill that fades fastest, and it comes back fastest with practice.
- Timed mixed practice. Only once patterns feel familiar, mix problems so you have to identify the pattern yourself.
- Talking while coding. The last step, and the one most people skip: narrating your approach, testing your code by hand and handling hints.
The patterns to refresh, in order
This order starts with the simpler patterns and builds toward the ones that depend on them. Our guide to LeetCode patterns for interviews covers each in depth.
| Pattern | Signal in the problem | Typical problem shape |
|---|---|---|
| Hash map counting and lookup | "Find a pair", "count", "first unique", duplicates | Two sum, anagram groups, frequency counts |
| Two pointers | Sorted input, pairs, in-place changes | Pair sums, removing duplicates, container problems |
| Sliding window | "Longest or shortest substring or subarray that..." | Longest substring without repeats, minimum window |
| Stack | Matching, "next greater", nested structure | Valid brackets, daily temperatures |
| Binary search | Sorted data, or "minimum value that works" | Search in rotated array, binary search on the answer |
| Trees: DFS and BFS | Hierarchies, levels, paths | Depth, level order, lowest common ancestor |
| Graphs: BFS, DFS, topological sort | Grids, dependencies, "shortest number of steps" | Number of islands, course schedule |
| Heap / top-k | "K largest", "k closest", merging sorted lists | Top k frequent elements, merge k lists |
| Intervals | Start and end times, overlaps | Merge intervals, meeting rooms |
| Backtracking | "All combinations", "all permutations" | Subsets, permutations, word search |
| Dynamic programming | "Number of ways", "maximum or minimum", overlapping choices | Climbing stairs, coin change, longest common subsequence |
For deeper refreshers on the harder rows, see graph algorithms for coding interviews and dynamic programming patterns. Keep the coding interview cheat sheet open while you work through the list.
A 3-week coding refresher plan
This is our suggested plan for an experienced engineer with one to two hours a day. If you have more time, stretch week 2; if you have less, see our 2-week coding interview plan.
| Week | Focus | Daily work | Milestone |
|---|---|---|---|
| Week 1 | Language, Big-O, easy patterns | 30 minutes of language drills; 2–3 easy problems from hash maps, two pointers, sliding window, stack and binary search; re-solve problems you have done before | You can write common data structure code without looking anything up |
| Week 2 | Medium patterns | 2 medium problems a day across trees, graphs, heaps, intervals and backtracking; after each, write one line on how you spotted the pattern | You can name the likely pattern within a few minutes of reading a problem |
| Week 3 | Mixed, timed and out loud | 1–2 random mediums against a 25–30 minute timer, explaining out loud; 2–3 full mock rounds; one or two dynamic programming problems | You finish most mediums in time and can explain and test your solution |
Which problem list should I use after a break?
Use one list and finish it, rather than sampling several. A rough guide:
- Two to three weeks: a 75-problem list such as the Blind 75 or the Grind 75, which cover the core patterns without much repetition.
- Four weeks or more: the NeetCode 150 roadmap, which adds more practice per pattern.
- A specific company: start from the list above, then add that company's commonly reported question types in the final week.
The number of problems matters less than whether you can explain why each solution works. Our guide to how many LeetCode problems to do before an interview explains why.
How do I practice coding out loud again?
A coding round is a conversation, and that part of the skill fades fastest when you have been coding quietly at work. Practice the full routine on every problem in week 3:
- Restate the problem and ask one or two clarifying questions (input size, edge cases, duplicates).
- Describe a brute-force approach and its complexity in one or two sentences.
- Explain the better approach before you write it.
- Code while narrating the main decisions, not every keystroke.
- Walk through a small example by hand and name the edge cases you tested.
Mock rounds are where this comes together. CoPilot Interview's Mock Interview can include coding questions in your chosen language, reads each question aloud, never auto-submits so you can think in silence, and scores your answer out of 10 with what to fix and a model answer. For the round format itself, see the coding interview copilot page.
If your first step is an online assessment, take the assessment yourself and follow the employer's rules — use CoPilot Interview to practice beforehand.
What has changed in coding interviews since you last interviewed?
The core format, solving a problem and explaining it in roughly 45–60 minutes, is still the norm. The biggest change to watch is how employers treat AI. In July 2025, Business Insider reported that Meta was testing a coding interview in which candidates can use an AI assistant that Meta provides, and a Meta spokesperson confirmed the test. Our page on the Meta AI-enabled coding interview covers what is known so far. Many employers still expect you to solve problems without outside help, so ask your recruiter what is allowed for each round and follow it.
If you were a heavy user of AI coding tools at work, spend part of week 1 coding with them switched off. Writing a heap or a graph traversal from memory is the part most people find has slipped.
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What should I study first for a coding interview after a break?
Start with your interview language and its standard library, then Big-O, then the core patterns such as hash maps, two pointers, sliding window, trees, graphs and heaps. Re-solve problems you have seen before. Leave hard new problems and timed practice for later.
How long does it take to get back into coding interview shape?
For an experienced engineer, about three weeks of one to two hours a day is a reasonable target for a standard coding round. If you have been away for several years or are aiming at very demanding interviews, plan for four to six weeks.
Should I use Blind 75 or NeetCode 150 after a break?
With two to three weeks, a 75-problem list like Blind 75 or Grind 75 covers the core patterns. With four weeks or more, NeetCode 150 adds more practice per pattern. Pick one list and finish it.
How many LeetCode problems should I do to refresh?
There is no magic number. As a rough guide, we suggest 40 to 75 problems spread across the core patterns. What matters more is that you can name the pattern, explain the solution and state its complexity.
Can I use AI in a coding interview now?
Only if the employer says so. In July 2025, Business Insider reported that Meta was testing a coding round with an AI assistant that Meta provides. Many employers still expect you to work without outside help, so ask your recruiter and follow their rules.
How do I practice explaining my code out loud?
On every practice problem, restate the problem, give a brute-force approach, explain the better approach before coding, narrate key decisions and test by hand. Timed mock interviews where you speak your answers are the closest practice to the real round.