Ace Technical Interviews: Data Structures to System Design
The four formats technical interviews take, the six problem patterns worth learning first, and an eight-week study plan.
The four interview formats
Most technical loops mix these. Knowing which one you are walking into decides what to rehearse.
Medium to hard
Mid-level and senior
All levels
Fundamentals
Six patterns to learn first
Most coding problems are a variation of one of these. Recognising the pattern is usually the hard part; the code follows.
Two pointers
Walk an array with two indices.
Valid Palindrome, 3Sum
Sliding window
Track a moving subarray or substring.
Longest Substring Without Repeats
BFS / DFS
Traverse graphs and trees.
Number of Islands
Binary search
Halve the search space on sorted or monotonic data.
Search in Rotated Sorted Array
Dynamic programming
Build the answer from overlapping subproblems.
Climbing Stairs, Knapsack
Backtracking
Explore choices and undo the ones that fail.
Permutations, N-Queens
An eight-week study plan
Fundamentals first, then structures, then the harder algorithm families, with the last two weeks reserved for design and mock interviews.
- Weeks 1–2
Fundamentals
15–20 hrs/week
- Weeks 3–4
Core data structures
15–20 hrs/week
- Weeks 5–6
Advanced algorithms
20–25 hrs/week
- Weeks 7–8
System design and mock interviews
20–25 hrs/week
Frequently asked questions
- How long should I prepare for a technical interview?
- Most candidates plan four to eight weeks of focused preparation, spending two or three hours a day on problems, data structures and system design. Add mock interviews in the final two weeks so you rehearse thinking aloud under time.
- What are the most important data structures for coding interviews?
- Arrays, hash maps, linked lists, trees (binary trees and BSTs in particular), graphs, stacks, queues and heaps. For each one, know the time and space cost of its common operations.
- What coding patterns should I learn first?
- Two pointers, sliding window, BFS/DFS, binary search, dynamic programming and backtracking. Most interview problems are a variation of one of these six, so learning to recognise them is the highest-leverage study you can do.
- How can an AI interviewer help with technical prep?
- It gives you somewhere to practise explaining an approach out loud and get feedback on the explanation — the part of a technical interview that solo problem-solving never rehearses.