How can you find a subarray with a given sum efficiently?
This classic problem requires finding a contiguous subarray whose elements sum to a target value. It tests sliding window techniques and hash map usage for prefix sums.
Why Interviewers Ask This
Interviewers use this to gauge a candidate's grasp of fundamental array algorithms. They want to see if the candidate can distinguish between positive-only arrays (sliding window) and general arrays (hash map). It also evaluates their ability to handle non-negative constraints mentioned in the prompt.
How to Answer This Question
Clarify if the array contains only non-negative numbers. If so, propose the sliding window approach for O(n) time. Otherwise, suggest using a hash map to store prefix sums and their indices. Explain how to calculate the difference between current and stored sums to find the target range quickly.
Key Points to Cover
- Sliding window application
- Non-negative constraint usage
- O(n) time complexity
- Pointer management
Sample Answer
Since the problem specifies non-negative numbers, I will use the sliding window technique. I maintain a window defined by start and end pointers, expanding the end to increase the sum and shrinking the start to decrease…
Common Mistakes to Avoid
- Using hash map unnecessarily for non-negative arrays
- Incorrect window shrinkage logic
- Failing to handle empty subarray cases
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