Data Structures You Must Know
December 10, 2025
Technical Tips5 min read
Essential Data Structures for Coding Interviews
According to an analysis of 10,000+ coding interview questions across FAANG companies, 8 core data structures appear in over 90% of problems. Mastering these data structures and knowing when to apply each one is the foundation of coding interview success.
Hash maps and arrays together appear in over 70% of coding interview problems. If you master only two data structures, master those.
The 8 Must-Know Data Structures
| Data Structure | Access | Search | Insert | Delete | Common Use |
|---|---|---|---|---|---|
| Array | O(1) | O(n) | O(n) | O(n) | Indexed access, iteration |
| Hash Map | O(1) | O(1) | O(1) | O(1) | Frequency counting, lookup |
| Linked List | O(n) | O(n) | O(1) | O(1) | LRU cache, ordered insertion |
| Stack | O(n) | O(n) | O(1) | O(1) | Parentheses matching, DFS |
| Queue | O(n) | O(n) | O(1) | O(1) | BFS, task scheduling |
| Binary Tree | O(log n) | O(log n) | O(log n) | O(log n) | Sorted data, range queries |
| Heap | O(1) top | O(n) | O(log n) | O(log n) | Priority queue, top-K |
| Graph | — | O(V+E) | O(1) | O(V+E) | Networks, paths, dependencies |
Pattern Recognition by Data Structure
- Array — Two pointers, sliding window, prefix sum. See array algorithms guide
- Hash Map — Two Sum pattern, frequency maps, anagram detection. See hash tables guide
- Tree — DFS (in/pre/post-order), BFS (level-order), BST validation. See tree algorithms guide
- Graph — BFS shortest path, DFS cycle detection, topological sort. See graph algorithms guide
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