The Counting Machine
A medium Python mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- Python
- Difficulty
- medium
- Seniority
- L4
Interview Prompt
Implement the iterator class `CountUp(values)` and the top-level driver `count_up(values)`. `CountUp` is a stateful iterator: iterating over it yields `values[i] * (i + 1)` for `i = 0 .. len(values) - 1` (1-based multiplier). It must implement the iterator protocol: `__iter__` returns the iterator and `__next__` produces the next transformed value, raising `StopIteration` once the values are exhausted. The test harness calls `count_up(values)`, where `values` is a list of integers. Construct a `CountUp` over `values`, drive it to completion (equivalent to `list(iter(CountUp(values)))`), and return the resulting list of integers in order. For an empty `values`, return an empty list `[]`.
Summary
It knows where it stopped last time.
How This Interview Works
- Read the vague prompt (just like a real interview)
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