How do you find the maximum sum of any contiguous subarray?
PICTURE THIS: ARRAY IN MEMORY
Index starts at 0. Scan once for max — O(n).
Simple meaning
Kadane's algorithm keeps a running sum, resetting it to the current value when the running sum goes negative, and tracks the global max.
WHY — Arrays instead of guessing?
Why interviewers care about Arrays:
question about Arrays.
trade-offs, and what you would actually do on a DSA project - not buzzwords.
Name the idea, why it exists, then one short example.
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:
- 1Kadane's algorithm keeps a
running sum, resetting it to the current value when the running sum goes negative, and tracks the global max.
- 2One O(n) pass and
O(1) space.
- 3If empty subarrays are
allowed the answer can be 0
- 4otherwise initialize with the
first element so all-negative arrays still work.
- 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:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Kadane's algorithm keeps a running sum, resetting it to the current value when the running sum goes negative, and tracks the global max. One O(n) pass and O(1) space.