Preparing for Coding Interviews
A six-week study plan for coding interviews: which patterns to learn in what order, how to talk through a solution, and how to rehearse under time.
What coding interviews draw from
The first four are asked at every level; the rest come in as the role gets more senior.
Data structures
Algorithms
Complexity analysis
Problem solving
System design basics
Networking
Concurrency
Object-oriented design
Six patterns to learn first
- Two Sum (sorted)
- Valid Palindrome
- Container With Most Water
- Maximum Subarray
- Longest Substring Without Repeats
- Minimum Window Substring
- Search in Rotated Sorted Array
- Find Peak Element
- Sqrt(x)
- Shortest Path
- Course Schedule
- Clone Graph
- Fibonacci
- Longest Common Subsequence
- Coin Change
- N-Queens
- Sudoku Solver
- Generate Parentheses
How to practise
Learn patterns, not solutions
Memorised answers fail on the first variation. Learn to recognise the pattern; the code follows from it.
Time every problem
Forty-five minutes is typical. Practising untimed trains a skill you will not be allowed to use.
Narrate the approach
The interviewer grades the reasoning as much as the result. Talk through the brute force, the bottleneck, and the improvement.
Step up the difficulty deliberately
Easy until they are quick, medium until they are reliable, hard only for the patterns you have already met.
A six-week plan
- Weeks 1–2
Foundation
- Revise arrays, linked lists, stacks and queues
- Solve around twenty easy problems
- Learn to state time and space complexity
- Run one mock interview for a baseline
- Weeks 3–4
Core algorithms
- Sorting, searching and the first four patterns
- Solve around thirty medium problems
- Introduce dynamic programming
- Run two mock interviews, narrating every solution
- Week 5
Advanced topics
- Trees, graphs and harder DP
- A handful of hard problems in patterns you know
- System design basics if the role is mid-level or above
- Run one mock interview
- Week 6
Rehearsal
- Review every pattern with one problem each
- Mixed problems under time
- Two full-length mock interviews
- Work on communication, not new material
The mock interviews in the plan are for the part problem sites cannot rehearse: explaining a solution to someone who is listening. A technical practice interview covers that; for the design rounds, see the system design guide.
Frequently asked questions
- How long does it take to prepare for coding interviews?
- Six to eight weeks of consistent practice is typical for someone with a computer science background who is rusty. Longer if the fundamentals are new; less if you interviewed recently.
- What topics should I focus on?
- Data structures and algorithms first, with complexity analysis, then the six patterns above. System design, networking and concurrency matter for mid-level and senior roles.
- What are the most common coding interview patterns?
- Two pointers, sliding window, binary search, graph traversal (BFS/DFS), dynamic programming and backtracking. Most interview problems are a variation of one of them.
- How does VirtualInterview.ai fit in?
- It rehearses the spoken half: an AI interviewer asks technical questions, follows up, and gives feedback on how you explained your approach. It does not run a problem bank with test cases — use a coding platform for that and the mock interviews for the conversation.