top of page
Data Structures
14 problems · Easy to Medium · Hash maps, stacks, and queues
Knowing which data structure to reach for — and why — is one of the most important skills in a technical interview. This track covers hash maps for O(1) lookup problems, stacks for bracket matching and expression evaluation, queues for BFS and streaming data, and culminates in two classic design problems: Circular Queue and LRU Cache.
Why it matters:
Data structure selection problems are a staple of phone screens at every major company because they reveal whether a candidate thinks about time complexity before writing code. A candidate who reaches for a hash map instinctively when they see a lookup problem thinks differently — and more efficiently — than one who defaults to nested loops.
bottom of page