What coding interviews actually test
A typical coding interview evaluates four things: your command of data structures and algorithms, how you break down and solve an unfamiliar problem, how clearly you communicate your thinking, and - in a separate round - your behaviour and experience. Senior roles add system design.
The reassuring part is that the technical content is finite and well-known. Most interview problems are variations on a small set of patterns, so targeted preparation goes a long way.
Master the core data structures and algorithms
- ✓Arrays and strings, hash maps, and two-pointer / sliding-window patterns.
- ✓Linked lists, stacks and queues.
- ✓Trees and graphs, with BFS and DFS traversals.
- ✓Sorting, binary search, and recursion.
- ✓Above all, time and space complexity (Big-O) - you'll be asked to analyse every solution.
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Follow a study plan
Structure beats random grinding. Learn one data structure or pattern at a time, solve a handful of problems on it, and only then move on. Revisit earlier topics using spaced repetition so they stay sharp.
Balance breadth and depth: it's better to deeply understand the common patterns than to superficially attempt hundreds of problems. Keep a log of problems you found hard and return to them.
Practise out loud and mock it
In a real interview you must think out loud - state your approach, discuss trade-offs, and narrate as you code. This is a skill that only develops through practice, so rehearse solving problems while explaining every step, ideally with a friend or in mock interviews.
Also prepare behavioural answers using concrete stories from your experience (a common framework is Situation, Task, Action, Result). Strong behavioural performance decides more offers than candidates expect.
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Common preparation mistakes
- ✓Grinding random problems without mastering the underlying patterns.
- ✓Solving silently instead of practising thinking out loud.
- ✓Ignoring Big-O analysis, which every interviewer asks about.
- ✓Skipping behavioural preparation until the night before.