The Tech Interview: LeetCode Hard, Job Easy
There's a famous gap in tech. To get the job, you prove you can solve a tricky algorithm puzzle under a timer while a stranger watches you sweat. Then you get the job and spend most of your first month figuring out why the staging environment is down and who owns the utils.py file with 4,000 lines.
Love it or hate it, the process exists. Here's how to prepare without losing your mind.
Understand what they're testing
Coding interviews usually test:
- problem solving: can you break a problem down?
- communication: can you explain your thinking while you work?
- coding fundamentals: loops, data structures, edge cases, complexity
- collaboration: do you take hints well, or argue with the interviewer?
The right answer matters, but how you get there often matters as much.
Learn patterns, not problems
There are thousands of practice problems and maybe 15–20 common patterns: two pointers, sliding window, hash maps for counting, BFS/DFS, binary search, heaps for "top k," dynamic programming for overlapping subproblems. Solve a few problems per pattern until you recognise them, rather than memorising 500 solutions.
Talk out loud
Silent coding is the most common mistake. Interviewers can't give credit for thinking they can't hear. A good rhythm:
- Repeat the problem in your own words, and ask clarifying questions.
- Walk through an example by hand.
- Describe a simple (even slow) approach first.
- Improve it, and state the time and space complexity.
- Code it, narrating as you go.
- Test with edge cases: empty input, one element, duplicates, huge values.
Don't neglect the other rounds
Behavioural interviews ("tell me about a time you disagreed with a teammate") are where many strong coders stumble. Prepare five or six real stories using the STAR structure: Situation, Task, Action, Result. Include at least one story about a mistake and what you learned.
System design (for mid-level and up): how would you design a URL shortener, a chat app, a news feed? Focus on requirements, trade-offs and bottlenecks, not on drawing every box.
Mock interviews are the cheat code
Practise with a friend or a mock interview platform. Being watched changes everything; you'll discover you forget basic syntax the moment someone is looking. Better to discover that with a friend than with a hiring manager.
When it goes badly
It will, sometimes. Interviews are noisy: a bad night's sleep, a weird question, an interviewer who's distracted. A rejection is often a sample of one bad hour, not a verdict on your ability. Write down the questions you struggled with, learn them and keep going.
The irony, embraced
Yes, you might never invert a binary tree at work. But the underlying skills (thinking clearly under pressure, explaining your reasoning, considering edge cases) are genuinely useful. And once you're hired, you can help make your company's interview process a bit more like the actual job. That's the real long game.