What Are Common Data Structures in Coding Interviews

Short answer

Interviews commonly test arrays, strings, hash maps, linked lists, stacks, queues, trees, graphs, and heaps. Knowing their operations and trade-offs is essential.

How it works

• Arrays/Strings: Indexed access, iteration, and two-pointer techniques.
• Hash Maps: O(1) lookups for counting and mapping relationships.
• Trees/Graphs: Traversal with DFS and BFS for hierarchical and networked data.
• Heaps: Efficient access to minimum or maximum elements.

Example

Finding the most frequent element in an array is trivial with a hash map but inefficient with nested loops.

Why it matters

The right data structure can reduce time complexity from O(n^2) to O(n). Interviewers assess whether you can select the appropriate tool for the problem.