What is the difference between std::vector and std::array?
PICTURE THIS: ARRAY IN MEMORY
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Index starts at 0. Scan once for max — O(n).
Simple meaning
vector is dynamic size on the heap
WHY — STL instead of guessing?
Why interviewers care about STL:
They want a clean
contrast on STL, not two memorised paragraphs.
Say what changes for
the developer, then one case where picking wrong hurts.
Stay structured
Name the idea, why it exists, then one short example.
Close cleanly
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1vector is dynamic size
on the heap
- 2array is fixed size
and can live on the stack.
- 3I use array when
N is known at compile time.
- 4vector is the default
growable buffer.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Say this line
“I use array when N is known at compile time.”
Break into beats
IusearraywhenNis
Speaking order
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Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
vector is dynamic size on the heap array is fixed size and can live on the stack.