Frequently Asked Problem Types by Data Structure
40 min · Intermediate
Most coding-round questions are variations of a few dozen classic problems, grouped by data structure and pattern. Knowing the groups lets you recognise a new problem quickly ("this is a sliding window") and plan your practice where it pays off most.
Topics in this lesson
- Arrays, strings, hashing, two pointers and sliding window: the fresher favourites
- Linked lists, stacks and queues, trees, graphs, heaps: the classic list
- DP and recursion questions at product companies
- Where to practise each in Section 7 Coding Challenges
- Pattern-recognition cues from the problem statement
Interview questions this lesson answers
- Which problem types come up most in fresher coding rounds?
- What extra topics appear in product-company rounds?
- How do you recognise a sliding-window problem?
- When does a sliding window not work for subarray sums?
- How do you recognise a two-pointer problem?
- How do you recognise a hashing problem?
- When is binary search the right tool besides sorted arrays?
- What is a monotonic stack and when do you use it?
- Which linked-list techniques should every candidate know?
- Which tree problems are most common?
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