Coding interviews feel infinite, but they're not. A surprisingly small set of patterns covers the overwhelming majority of what gets asked. If you order your study by frequency rather than by textbook chapter, you become interview-ready far sooner — because you're solid on the high-probability material before you've touched the rare stuff.

Here are the 21 topics, grouped by how often they actually appear.

Tier 1 — Show up constantly (master these first)

1. Arrays & strings — the substrate of everything.
2. Hashing / hash maps — the single highest-leverage tool.
3. Two pointers
4. Sliding window
5. Binary search — and its sneaky "search on answer" variant.
6. Sorting — plus knowing when not to sort.
7. Recursion & backtracking

Tier 2 — Show up often (master before any real interview)

8. Linked lists
9. Stacks & queues (incl. monotonic stack)
10. Trees — traversals, BST properties.
11. Heaps / priority queues — top-K is everywhere.
12. Graphs — BFS, DFS, topological sort.
13. Dynamic programming — the 1D and 2D classics.
14. Greedy
15. Intervals

Tier 3 — Show up sometimes (role- and level-dependent)

16. Bit manipulation
17. Tries
18. Union-Find (DSU)
19. Shortest paths (Dijkstra, Bellman-Ford)
20. Advanced DP (DP on trees, bitmask DP)
21. Segment trees / Fenwick trees — rare outside competitive-leaning loops.

How to spend your time

Spend roughly half your prep on Tier 1, a third on Tier 2, and only what's left on Tier 3. The common failure is inverting this — burning weeks on segment trees while shaky on hashing. Interviewers sample from the top of this list far more than the bottom.

Your target role shifts a few items up or down (backend pulls graphs up; frontend pulls them down), but Tier 1 is universal. Anchor there, then specialise. If you want this sequencing handled for you — across the Apna College, Love Babbar, and Striver sheets at once — that's what SUITS does.