Build a decision tree classifier from scratch: pick splits by Gini or entropy, then predict.
A from-scratch classic that checks recursion plus the split criterion math. The signal is computing impurity correctly, picking the best threshold by information gain, and knowing the stopping rules. Here is a clean recursive implementation.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
A from-scratch classic that checks recursion plus the split criterion math. The signal is computing impurity correctly, picking the best threshold by information gain, and knowing the stopping rules. Here is a clean recursive implementation.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
