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The Truth About LeetCode: It's Just An IQ Test
LeetCode is not useless. It is also not engineering interview in full.
It is closer to IQ test with syntax. It measures pattern recognition, speed, edge-case discipline, and stress handling. Useful signals. Incomplete signals.
What LeetCode Proves
If candidate can solve tree, graph, heap, and dynamic programming problems under pressure, they probably have strong raw problem-solving ability.
As ICPC person, I respect this. Fast algorithmic brain is real advantage.
But inverting binary tree does not prove you can design payment API, migrate database, debug latency spike, or write readable service for team.
What It Does Not Prove
It does not prove taste. It does not prove testing habits. It does not prove product thinking. It does not prove ability to say “I do not know”. It does not prove you can maintain code after six months.
Contest-style code often optimizes for accepted answer, not future human.
Interview Problem
Many companies use LeetCode because it is easy to standardize. System design and code review interviews require trained interviewers. Algorithm puzzle is cheaper.
Cheap signal becomes gate. Then candidates optimize for gate. Then everyone pretends this is science.
What Actually Matters
For backend roles I care about:
- Can you explain trade-offs?
- Can you model data correctly?
- Can you write tests before risky code?
- Can you reason about failure modes?
- Can you communicate under uncertainty?
- Can you simplify instead of showing off?
Algorithms help. They are not enough.
How To Use LeetCode Well
Train it like gym. Learn patterns: two pointers, sliding window, BFS, DFS, heap, union-find, DP. Practice explaining complexity.
Then stop making it identity.
Build real systems. Read production code. Learn SQL. Learn HTTP. Learn observability. Learn tests.
Final Verdict
LeetCode is decent filter for raw reasoning and bad filter for full engineering maturity.
If you pass it, good. If you only pass it, still not enough.